Electrolytic test machine

ABSTRACT

An electrolytic test machine is used for a corrosion resistance test for a test material comprised of a metal blank and a coating film. The electrolytic test machine is constructed so that an adverse influence, due to chlorine gas generated during a test, can be inhibited. The electrolytic test machine includes an electrolytic cell in which an aqueous solution of NaCl is stored so that a test material is immersed in the aqueous solution of NaCl. An electrode is immersed in the aqueous solution of NaCl. A DC power source supplies electric current between the electrode and the test material. A chlorine gas treating device collects chlorine gas which is generated with electrolysis of the aqueous solution of NaCl and which is released out of the aqueous solution of NaCl along with the aqueous solution of NaCl. The chlorine gas treating device includes a treating pipe line, a suction pump mounted on the treating pipe line, and a chlorine gas purifying member.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electrolytic test machine, and inparticular relates to an electrolytic test machine including anelectrolytic cell in which an aqueous solution of NaCl is stored so thata test material can be immersed in the aqueous solution of NaCl, anelectrode immersed in the aqueous solution of NaCl, and a DC powersource for supplying electric current between the electrode and the testmaterial.

2. Description of the Related Art

Such an electrolytic test machine is used, for example, for a cathodepeel-off test for a coating film on a test material (see Japanese PatentApplication Laid-open No.195612/1995). This test is carried out in sucha manner that the polarity of the test material is set at a cathode,while the polarity of the electrode is set at an anode. Therefore, achlorine gas is produced on the side of the electrode with electrolysisof the aqueous solution of NaCl.

In this case, such a measure may be contemplated that a chlorine gastreating means collects and treats the chlorine gas that is released outof the aqueous solution of NaCl and flows within the electrolytic cell.

However, if the chlorine gas treating means of the above-described typeis used, it is impossible to inhibit the production of HC10 and NaClo inthe aqueous solution of NaCl and impossible to inhibit the dissolutionof the chlorine gas into the aqueous solution of NaCl.

As a result, a problem arises because the coating film is whitened bythe bleaching effects of HClO and NaClO, and the appearance of thecoating film is considerably different from a corroded state in anatural environment. Another problem that arises is that theconcentration of chlorine in the aqueous solution of NaCl is increasedand hence, an irritant odor is generated during replacement of the testmaterial or during replacement of the aqueous solution of NaCl whichdegrades the working environment.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide anelectrolytic test machine, wherein the production of HClO and NaClO inthe aqueous solution of NaCl and the dissolution of the chlorine gasinto the aqueous solution of NaCl can be inhibited to the maximumamount.

To achieve the above object, according to a first aspect and feature ofthe present invention, there is provided an electrolytic test machinecomprising an electrolytic cell in which an aqueous solution of NaCl isstored so that a test material can be immersed in the aqueous solutionof NaCl. An electrode is immersed in the aqueous solution of NaCl. A DCpower source supplies electric current between the electrode and thetest material. The electrolytic test machine further includes a chlorinegas treating device which collects, out of the aqueous solution of NaCl,chlorine gas which is generated around the electrode with electrolysisof the aqueous solution of NaCl along with the aqueous solution of NaCl.

With the above arrangement, the chlorine gas generated in the aqueoussolution of NaCl can be immediately collected and treated. Therefore,the diffusion of the chlorine gas into the aqueous solution of NaCl inthe electrolytic cell can be suppressed. Thus, the production of HClOand NaClO in the aqueous solution of NaCl in the electrolytic cell isinhibited, the dissolution of the chlorine gas into the aqueous solutionof NaCl is inhibited to the utmost and the decomposition of thecollected chlorine gas is realized.

In addition, according to the present invention, the chlorine gastreating device includes a treating pipe line having a suction portdisposed in an electrode immersion zone within the electrolytic cell, asuction pump disposed in the treating pipe line, and a chlorine gaspurifying member disposed in the treating pipe line and having acatalyst which has a function to decompose NaClO and HClO which arereaction products in a test.

With the above arrangement, it is possible to reliably perform thedecomposition of NaClO and HClO which are reaction products.

Further, according to the present invention, the electrolytic testmachine further includes an NaOH introducing device, mounted in theelectrolytic cell, for introducing NaOH to the electrode immersion zone.NaOH is produced in the test material immersion zone within theelectrolytic cell.

With the above arrangement, it is possible to promote the decompositionof the collected chlorine gas and to prolong the life of the catalyst.

The above and other objects, features and advantages of the inventionwill become apparent from the following description of the preferredembodiment taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic illustration of an electrolytic test machine;

FIG. 2 is a perspective view of a test material;

FIG. 3 is a sectional view taken along a line 3--3 in FIG. 2.;

FIG. 4 is a perspective view of the electrolytic test machine;

FIG. 5 is a front view of the electrolytic test machine, whichcorresponds to a view taken along an arrow 5 in FIG. 4;

FIG. 6 is a view taken along an arrow 6 in FIG. 5;

FIG. 7 is a vertical sectional front view of the electrolytic testmachine, which corresponds to a sectional view taken along a line 7--7in FIG. 6;

FIG. 8 is a cutaway plan view of an essential portion of theelectrolytic test machine, which corresponds to a sectional view takenalong a line 8--8 in FIG. 7;

FIG. 9 is a sectional view taken along a line 9--9 in FIG. 7;

FIG. 10 is a perspective view illustrating the relationship among anelectrolytic cell, a cover and a hood;

FIG. 11 is a sectional view taken along a line 11--11 in FIG. 7;

FIG. 12 is a sectional view taken along a line 12--12 in FIG. 8;

FIG. 13 is a sectional view taken along a line 13--13 in FIG. 7;

FIG. 14 is an illustration of a piping in the electrolytic test machine;

FIG. 15 is an illustration of a wiring in the electrolytic test machine;

FIG. 16 is a sectional view showing the structure of a connection of acarbon electrode with an electric feeder wire;

FIG. 17 is an illustration for explaining a corrosion resistance test:

FIG. 18 is a perspective view showing the connection of the testmaterial with an energizing terminal base;

FIG. 19 is a graph illustrating the relationship between the appliedvoltage and the width of peeling-off of a coating film from a damagedportion of the test material;

FIG. 20 is a graph illustrating the relationship between the cycle andthe width of peeling-off of the coating film from the damaged portion ofthe test material;

FIG. 21 is a graph illustrating the relationship between the cycle andthe maximum decrement in plate thickness of the test material;

FIG. 22 a block diagram of a determining device for determining areplacement time of the carbon electrode;

FIG. 23 is a flow chart illustrating the operation of the determiningdevice for determining the replacement time of the carbon electrode;.

FIG. 24 is a diagram for explaining a remaining effective currentquantity indicating portion;

FIG. 25 is a perspective view of a central cover;

FIG. 26 is a sectional view taken along a line 26--26 in FIG. 6;

FIG. 27 is a sectional view taken along a line 27--27 in FIG. 6.

FIG. 28 is a sectional view taken along a line 28--28 in FIG. 7;

FIG. 29 is a sectional view taken along a line 29--29 in FIG. 11;

FIG. 30 is a graph illustrating a first example of the relationshipbetween the test time and the effective concentration of chlorine;

FIG. 31 is a graph illustrating a second example of the relationshipbetween the test time and the effective concentration of chlorine;

FIG. 32 is a graph illustrating a third example of the relationshipbetween the test time and the effective concentration of chlorine;

FIG. 33 is an illustration of a piping in the electrolytic test machine;

FIG. 34 is a graph illustrating a first example of the relationshipbetween the test time and the concentration of a chlorine gas;

FIG. 35 is a block diagram of an abnormal-point detector in a chlorinegas treating device;

FIG. 36 is a graph illustrating the relationship between the situationof a treating system and the flow rate;

FIG. 37 is a flow chart illustrating the operation of the abnormal-pointdetector;

FIG. 38 is a vertical sectional side view of a chlorine gas purifyingmember, which corresponds to a sectional view taken along a line 38--38in FIG. 7;

FIG. 39 is an end view of a catalyst unit, which corresponds to a viewtaken along a line 39--39 in FIG. 38;

FIG. 40 is an end view of a lid, which corresponds to a view taken alonga line 40--40 in FIG. 38;

FIG. 41 is a block diagram of a determining device for determining areplacement time of a catalyst;

FIG. 42 is a flow chart illustrating the operation of the determiningdevice for determining the replacement time of the catalyst;

FIG. 43 is a sectional view taken along a line 43--43 in FIG. 9;

FIG. 44 is a diagram showing one example of an abnormality-generationdetecting means in an exhaust system;

FIG. 45 is a graph illustrating a second example of the relationshipbetween the test time and the concentration of the chlorine gas;

FIG. 46 is a graph illustrating a third example of the relationshipbetween the test time and the concentration of the chlorine gas;

FIG. 47A is a diagram for explaining the positions of liquid levelsensors disposed in the abnormal-point detector in the exhaust system;

FIG. 47B is a block diagram of the abnormal-point detector in theexhaust system;

FIG. 48 is a graph illustrating the relationship between the situationof the exhaust system and the liquid level;

FIG. 49 is a flow chart illustrating the operation of the abnormal-pointdetector;

FIG. 50 is a diagram showing another example of anabnormallty-generation detecting means in the exhaust system;

FIG. 51 is a sectional view taken along a line 51--51 in FIG. 7;

FIG. 52 is a block diagram showing another example of a determiningdevice for determining a replacement time of the carbon electrode;

FIG. 53 is a flow chart illustrating the operation of the other exampleof the determining device for determining the replacement time of thecarbon electrode;

FIG. 54 is a block diagram showing another example of a determiningdevice for determining a replacement time of the catalyst; and

FIG. 55 is a block diagram showing a further example of a determiningdevice for determining a replacement time of the catalyst.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A. Summary of Electrolytic Test Machine

An electrolytic test machine 1 shown in FIG. 1 is used for a corrosiontest for a test material 2 shown in FIGS. 2 and 3. The test material 2is comprised of a steel plate 3 such as a metal blank, and a coatingfilm 4 formed on the entire steel plate 3.

The electrolytic test machine 1 includes an electrolytic device 5. Aharmful gas treating device 6, an exhaust device 7 and an overflowdevice 8 having a sucking function are mounted to the electrolyticdevice 5.

The electrolytic device 5 includes a DC power source 9 (aconstant-voltage power source having a highest voltage of 20 V and amaximum current of 50 A), a computer programmed control unit 10, anelectrolytic cell 12 in which an aqueous solution of NaCl 11 as anelectrolytic liquid is stored, a plate-like carbon electrode 13 which isa consumable electrode as an electrolytic electrode immersed in theaqueous solution 11 of NaCl, an electric heater 14, a water level sensor15, a temperature sensor 16, a water supply pipe line 17 and a drainagepipe line 18.

Because an aqueous solution of NaCl 11 is used, a chlorine gas isgenerated with the electrolysis of the aqueous solution of NaCl 11during a test. To cope with this, an upward opening 19 in theelectrolytic cell 12 is covered and sealed with a cover 20 made of asynthetic resin. An upward opening 21 in the cover 20 is used forplacing and removing the test material 2 into and out of theelectrolytic cell 12. The opening 21 is sealed with an openable andclosable lid 22. The lid 22 and cover 20 tightly close the electrolyticcell 12.

An electric power cylinder 23, which is a drive source for opening andclosing the lid 22, is supplied with an electric current from anexternal power source.

The test material 2 is hung from a support bar 24 in the electrolyticcell 12 by a string 25 made of a synthetic resin, and is immersed intothe aqueous solution of NaCl 11. The carbon electrode 13 and the steelplate 3 of the test material 2 are connected to the DC power sourcethrough energizing lines 26 and 27. A polarity switch-over relay 28, asa polarity switch-over means, is connected to the energizing lines 26and 27. An ammeter 29 is connected to one of the energizing lines 27between the DC power source 9 and the polarity switch-over relay 28.

The DC power source 9 is controlled at a constant voltage by the controlunit 10 and also controlled in an ON/OFF manner. The polarityswitch-over relay 28 is controlled so that the polarity of the steelplate 3 of the test material 2 is alternately switched over frompositive to negative polarity or vice versa. In this case, the polarityof the carbon electrode 13 is, of course, opposite from that of thesteel plate 3. The ammeter 29 inputs an electric current flowing acrossthe carbon electrode 13 and the steel plate 3 to the control unit 10.

The water supply pipe line 17 communicates at one end thereof with acock 30 of a water service which is a water supply source and at theother end with the electrolytic cell 12. A solenoid valve 31 is mountedat an intermediate portion of the water supply pipe line 17. The openingand closing of the solenoid valve 31 are controlled through the controlunit 10 by a detection signal from the water level sensor 15. Thedrainage pipe line 18 communicates with a bottom of the electrolyticcell 12 and includes a manual cock 32.

The electric heater 14 is supplied with an electric current from theexternal power source and is controlled in an ON/OFF manner through thecontrol unit 10 by detection signals from the water level sensor 15 andthe temperature sensor 16.

The chlorine gas treating device 6 includes a treating pipe line 33extending from the electrolytic cell 12. An electric suction pump 34, achlorine gas purifying member 35 and an abnormal-point detecting flowrate sensor 36 are mounted in the treating pipe line 33. The suctionpump 34 is supplied with an electric current from the external powersource.

The exhaust device 7 includes an exhaust pipe line 37 extending from theelectrolytic cell 12. A chlorine gas adsorbing member 38, an electricexhaust fan 39 and a detecting means 40 for detecting an abnormalitygeneration are provided in the exhaust pipe line 37. The exhaust fan 39is supplied with an electric current from the external power source.

The overflow device 8, having a sucking function, is comprised of anoverflow pipe 41 extending from the electrolytic cell 12, a gas intakeport 42 provided in the overflow pipe 41, and a chlorine gas (harmfulgas) adsorbing member 43 disposed in an inlet of the overflow pipe 41.

B. Entire structure of Electrolytic Test Machine (FIGS. 4 to 9)

The electrolytic test machine 1 is constructed into a movable type,wherein the side thereof as viewed in FIGS. 4 to 6, 8 and 9 is a frontportion X. Therefore, testing personnel conducts a testing operationfrom the front portion X.

As shown in FIGS. 5 to 9, the electrolytic test machine 1 includes arectangular machine base 44. A plurality of casters 45, functioning astraveling wheels, are mounted on a lower surface at the four corners ofthe machine base 44 in the illustrated embodiment. If the direction a ofmovement of the machine base 44 is a lengthwise direction, namely, alateral direction, a tracklng/urging hook 46 is provided on eachopposite outer end face of the machine base 44 as viewed in thedirection of movement of the machine base 44, namely, on left and rightend faces.

A mechanical section M is disposed on the machine base 44 on one endside, i.e., on the right side as viewed in FIG. 7 and 8 along thedirection a of movement of the machine base 44. A box-like electrolyticbell 12 made of a synthetic resin is disposed at a central portion ofthe machine base. A control section C is disposed on the machine base 44on the other end side, e.g., on the left side as viewed in FIGS. 7 and8.

The electrolytic cell 12 is detachably mounted to the machine base 44through a pair of mounting plates 50 which protrude from lower ends ofan outer surface of left and right sidewall portions 48 and 49 of aperipheral wall 47, as shown in FIGS. 7 and 8.

The electrolytic cell 12, the mechanical section M and the controlsection C are covered respectively with a central cover section 51, aleft cover section 52 and a right cover section 53 which constitute acover 20 made of a synthetic resin. The central cover section 51covering the electrolytic cell 12 seals the upward opening in theelectrolytic cell 12, and has a rectangular opening 21 which is used forplacing and removing the test material 2 into and out of theelectrolytic cell 12. The lid 22, for opening and closing the opening21, has a hinge on the side of one end thereof, namely, on the side of arear portion thereof.

As best shown in FIGS. 7 and 9, included in the mechanical section M arean electric power cylinder 23, which is the drive source for opening andclosing the lid 22, a suction pump 34 and a chlorine gas purifyingdevice 35 in the chlorine gas treating device 6, an exhaust fan 39 ofthe exhaust device 7, and the like.

In addition, as best shown in FIGS. 7 and 8, included in the controlsection C are transformers (not shown), various switches and the likefor the suction pump 34 and the exhaust fan 39, in addition to the DCpower source 9, the computer programmed control unit 10 and the polarityswitch-over relay 28.

With such a construction, the electrolytic cell 12 is independent fromthe mechanical section M and the control section C. Therefore, it ispossible to sufficiently increase the volume of the electrolytic cell12, thereby moderating the limitation for the size of the test material2.

The electrolytic cell 12, the mechanical section M and the controlsection C are independent from one another, resulting in independentmaintenance for them.

Further, the electrolytic test machine 1 is of a movable type andtherefore, it is easy to transport the test machine 1 into and out of atest room.

Moreover, the relatively large-sized and heavy electrolytic cell 12 isdisposed at the central area and therefore, the electrolytic testmachine 1 is stable and balanced when moved.

Additionally, the electrolytic cell 12, the mechanical section M and thecontrol section C are disposed in a line in the direction a of movementof the electrolytic test machine 1 and therefore, the width dimensionperpendicular to the direction a of movement can be easily adjusted tothe width dimension of an access port of a ready-made test room. Forexample, the width b in the electrolytic test machine 1 is set at 800mm, and the length c can be set at 1,600 mm, as shown in FIG. 6.

C. Structure of Disposition of Carbon Electrode and Electric Heater(FIGS. 7, 8 and 10 to 13)

In a left and lower area within the electrolytic cell 12, an electrodechamber 55 is immersed in the aqueous solution of NaCl 11. The electrodechamber 55 is defined by the peripheral wall 47 of the electrolytic cell12, and a partition plate 54. The partition plate 54 is opposed to andin proximity to an inner surface of the peripheral wall 47 and isattachable to and detachable from the electrolytic cell 12.

The left sidewall portion 48 of the peripheral wall 47 has a divisionplate 56, made of a synthetic resin, which forms a rear wall of theelectrode chamber 55. A front wall portion 57 of the peripheral wall 47has a projection 58 which forms a front wall of the electrode chamber 55and is opposed to the division plate 56. The partition plate 54 isslidably fitted into opposed guide grooves 59 and 60 in the divisionplate 56 and the protection 58. Therefore, the partition plate 54 formsa right wall of the electrode chamber 55, while the left sidewallportion 48 forms a left wall of the electrode chamber 55.

The plate-like carbon electrode 13 is accommodated within the electrodechamber 55 in a vertical state and in parallel to the partition plate54. An upper portion of the carbon electrode 13 protrudes above the topend of the partition plate 54. Front and rear end faces of the carbonelectrode 13 are clamped by clamping member 62 of a protruding plate 61of the left sidewall portion 48 and by clamping member 63 of the frontwall portion 57. The left and right flat sides of the carbon electrode13 are clamped by a pair of clamping members 64 of the left sidewallportion 48 and a pair of clamping members 65 of the partition plate 54.The carbon electrode 13 is capable of being set between and withdrawnfrom between the clamping members 62 to 65. In order to guide theinsertion of the electrode 13, a slope d is formed on an upper portionof each of the clamping members on the insertion side of the electrode.The partition plate 54 has a large number of through-holes 66 atlocations opposed to the carbon electrode 13 for permitting the aqueoussolution of NaCl 11 to be passed therethrough.

In a right lower area within the electrolytic cell 12, another electrodechamber 55, similar to the above-described electrode chamber 55, isdefined utilizing the right sidewall portion 49 of the peripheral wall47. Another plate-like carbon electrode 13, similar to theabove-described electrode 13, is accommodated in the other electrodechamber 55. Thus, the distribution of voltage in the test material 2 canbe uniform. Components of the right electrode chamber 55 similar tothose of the left electrode chamber 55 are designated by like referencecharacters.

In a rear area within the electrolytic cell 12, a heater chamber 68 isdefined by the peripheral wall 47 of the electrolytic cell 12 and apartition plate 67. The partition plate 67 is opposed to and inproximity to the inner surface of the peripheral wall 47 and isattachable to and, detachable from the electrolytic cell 12. Thepartition plate 67 has a plurality of through-holes 69 for permittingthe aqueous solution of NaCl 11 to be passed therethrough, and isslidably fitted into opposed guide grooves 70 defined in the pair ofdivision plates 56 of both electrode chambers 55. Therefore, a frontwall of the heater chamber 68 is formed by the partition plate 67 andthe pair of division plates 56, A rear wall of the heater chamber 68 isformed by a rear wall portion 71 of the peripheral wall 47 and left andright walls of the heater chamber 68 are formed by the left and rightsidewall portions 48 and 49.

As best shown in FIGS. 7, 8, 12 and 13, the pair of electric heaters 14are accommodated within the heater chamber 68 at a predetermineddistance in left and right directions and with their coiled portions eturned downwards. An upper portion of each of electric heaters 14 issupported by a support 72 mounted on the rear wall portion 71 above theliquid level f of the aqueous solution of NaCl 11. The temperaturesensor 16, for detecting the temperature of the aqueous solution of NaCl11, is disposed between both electric heaters 14. The temperature sensor16 has a lower end portion immersed in the aqueous solution of NaCl 11,and an upper portion supported by a support 73 mounted on the rear wallportion 71 above the liquid level f.

Within the electrolytic cell 12, an area surrounded by the threepartition plates 54 and 67 and the front wall portion 57 is used as aspace g for placement of the test material 2.

As shown in FIGS. 7, 8 and 13, a U-shaped support 74 is projectinglyprovided on an inner surface of the front wall portion 57, so that it islocated above the liquid level f of the aqueous solution of NaCl 11 andis located at a laterally intermediate portion. A recess 77 is definedby a pair of protrusions 76 located at a stepped portion 75 of thepartition plate 67 adjacent the heater chamber 68. Thus, the recess 77is opposed to the support 74. The test material supporting bar 24, madeof a synthetic resin and having a channel-like shape, is detachablysuspended between the U-shaped support 74 and the recess 77. As shown inFIGS. 1 and 13, the test material 2 is immersed into the aqueoussolution of NaCl 11 in such a manner that it is hung from the supportingbar 24 through a looped portion h of a string of a synthetic resinattached to the test material 2.

If both carbon electrodes 13 and both electric heaters 14 areaccommodated within the electrode chambers 55 and the heater chamber 68as described above, the contact of the electrodes 13 and the electricheaters 14 with the test material 2 can be reliably prevented, and bothcarbon electrodes 13 and both electric heaters 14 can be protected. Eachof the partition plates 54 and 67 are in proximity to the peripheralwall 47 of the electrolytic cell 12 and moreover, each of the electrodechambers 55 and the heater chamber 68 uses a portion of the peripheralwall 47 as a portion of the chamber wall. Therefore, the space g forplacement of the test material 2 can be made wider, as compared withwhen another partition plate is used in place of the peripheral wall 47.Each of the partition plates 54 and 67 can be removed from theelectrolytic cell 12 and each of the carbon electrodes 13 can be removedfrom the electrolytic cell 12. Therefore, the partition plates 54 and 67and the carbon electrodes 13 cannot become obstacles in carrying outmaintenance, for example, washing the inside of the electrolytic cell12, resulting in easy maintenance of the cell 12. Since each of thecarbon electrodes 13 is clamped by the peripheral wall 47 and thepartition plate 54, the structure of supporting the carbon electrode 13is simple and secure. Also, since each of the electric heaters 14 isattached to the fixed peripheral wall 47, the structure of attaching theelectric heater 14 is secure. The three partition plates 54 and 67 maybe formed into a U-shaped integral configuration.

D. Water-supply and Discharge Structure of Electrolytic Cell (FIGS. 7,8, 10, 13 and 14)

Above the heater chamber 68, an L-shaped water supply pipe 79, made of asynthetic resin pipe material, in the water supply pipe line 17 isdisposed in the left sidewall portion 48 of the electrolytic cell 12with its outlet turned downwards. A tube 80, made of a soft syntheticresin, is attached to the water supply pipe 79, as best shown in FIG.10, and has a lower end portion loosely inserted into a retaining sleeve81 made of a synthetic resin. The sleeve 81 is mounted to a rear surfaceof the division plate 56 adjacent the heater chamber 68. The retainingsleeve 81 prevents the lower end portion of the tube 80 from beingunnecessarily swung during supplying of water. The tube 80 can bewithdrawn from the retaining sleeve 81 and used for washing theelectrolytic cell 12.

As best shown in FIGS. 8 and 14, half of the water supply pipe line 17,on the side of the water supply pipe 79, is connected to a water supplyportion 82a of a water dispensing block 82, which is mounted on themachine base 44 via outer surfaces of the left sidewall portion 48 andthe rear wall portion 71, and half of the supply pipe line 17 on theside of the cock 30 for water service is connected to the water supplyportion 82a. In the half of the water supply pipe line 17 on the side ofthe water supply pipe 79, a solenoid valve 31 is mounted at anintermediate portion thereof. The preparation of the aqueous solution ofNaCl 11 is carried out within the electrolytic cell 12 after supplyingwater to the electrolytic cell 12.

A drainage port 84 is opened in a central portion of a bottom wall 83 ofthe electrolytic cell 12. A drainage pipe line 18, made of a syntheticresin pipe material, is connected to the drainage port 84. Half of thedrainage pipe line 18, on the side of the drainage port 84, is passedthrough the inside of the machine base 44 and connected to a drainageportion 82b of the water dispensing block 82. Half of the drainage pipeline 18 on the side of a drainage channel 86 is connected to thedrainage portion 82b. In the half of the drainage pipe line 18 on theside of the drainage port 84, the manual cock 32 is mounted at anintermediate portion thereof.

E. Control of Water Level of Electrolytic Cell (FIGS. 7 and 8)

The water level sensor 15, for controlling the amount of the aqueoussolution of NaCl 11, is disposed at the right end of the inner surfaceof the rear wall portion 71 of the electrolytic cell 12. The water levelsensor 15 includes first, second and third detecting elements i, j and kextending vertically and a level of their lower ends is different fromone another. These detecting elements are supported on a support 87mounted on the rear wall portion 71 and located above the liquid level fof the aqueous solution of NaCl 11. The lower end of the first detectingelement i lies at a highest position. The lower end of the thirddetecting element k lies at a lowest position and the lower end of thesecond detecting element j lies at a middle position between both thelower ends of the first and third detecting elements i and k.

During supplying of water to the electrolytic cell 12, the first andthird detecting elements i and j are non-conducting therebetween, andthe solenoid valve 31 is controlled into an opened state by the controlunit 10. If the liquid level f rises up to the lower end of the firstdetecting element i, the first and third detecting elements i and j arebrought into conduction therebetween, and the solenoid valve 31 iscontrolled into a closed state by the control unit 10. This causes thewater supply to be stopped. If the liquid level f is low and spacedapart from the lower end of the first detecting element i during a test,the first and third detecting elements i and j are brought intonon-conducting therebetween, and the solenoid valve 31 is brought intoan opened state, thereby permitting water to be supplied. In thismanner, the amount of aqueous solution of NaCl 11 is usually controlledby the first detecting element i.

On the other hand, if water is not supplied even if the liquid level fis spaced apart from the lower end of the first detecting element I,because the first detecting element i fails to operate in the test, thesecond and third detecting elements j and k are brought intonon-conduction therebetween when the liquid level f is lower and isspaced apart from the lower end of the second detecting element j. TheDC power source 9 is therefore controlled into an OFF state by thecontrol unit 10. This causes electric current supplied to the carbonelectrodes 13 and the test material 2 to be cut off, thereby stoppingthe test.

The second and third detecting elements j and k are also used for thecontrol of both electric heaters 14. More specifically, if the aqueoussolution of NaCl 11 is in a defined amount, the lower ends of the secondand third detecting elements j and k are located in the aqueous solutionof NaCl 11, and the second and third detecting elements j and k are inconduction therebetween. Hence, both the electric heaters 14 arecontrolled into energized states by the control unit 10. For example, ifthe liquid level f is spaced apart from the lower end of the seconddetecting element j, the second and third detecting elements j and k arebrought into non-conduction therebetween. Hence, both electric heaters14 are controlled into energization-stopped states by the control unit10.

F. Structure of Wiring of Carbon Electrode and Energizing Terminal Basefor Test Material (FIGS. 8, 9, 11, 13 and 15)

In the front wall portion 57 of the electrolytic cell 12, a receivingmember 88, made of a synthetic resin, having a channel-likeconfiguration is fixed to extend laterally above the U-shaped support74.

As best shown in FIGS. 8 and 9, a vertical and quadrilateral frame 90 inthe machine base 44 extends the outer surface of the right sidewallportion 49 of the electrolytic cell 12. A terminal box 92 is fixed to anupper surface of a lower angle member 91 which extends longitudinally ofthe frame 90.

Referring to FIGS. 11, 13 and 15, feeder wires 93 are connected to frontand rear sides of the upper portions of the left and right carbonelectrodes 13, respectively. The two feeder wires 93 of each carbonelectrode 13 are drawn to the outside of the electrode chamber 55through a notch 94 of each partition plate 54. As shown in FIGS. 9 and15, the feeder wires 93 are passed into the inside of the receivingmember 88 from notches 95 of the receiving members 88, where they arecollected into four wires. The feeder wires 93 are drawn through agrommet 96 of the right sidewall portion 49 to the outside of theelectrolytic cell 12 and connected to connection terminals of theterminal box 92. Main 97 connected to the connection terminals of theterminal box 92 is drawn from the terminal box 92. The main 97 isextended along the outer surfaces of the right sidewall portion 49, therear wall portion 71 and the left sidewall portion 48 of theelectrolytic cell 12, and connected to DC power source 9 through thepolarity switch-over relay 28. The feeder wires 93, the terminal box 92and the main 97 constitute one of the energizing line 26.

Referring again to FIGS. 8, 13 and 15, an energizing terminal base 98,made of titanium, used for connection to the test material 2 is mountedon the front wall portion 57 of the electrolytic cell 12 to lie belowthe receiving member 88 and in the vicinity of the U-shaped support 74.A first connecting portion 99 of the energizing terminal base 98 withthe test material 2 is disposed within the electrolytic cell 12, and asecond connecting portion 100 of the energizing terminal base 98 withthe DC power source 9 is disposed outside the electrolytic cell 12. Aplurality of connecting bores 101, each having an internal thread, aredefined in the first connecting portion 99, so that they correspond tothe plurality of feeder wires 103 connected to a plurality of testmaterials 2. A main 102 is connected to the second connecting portion100. The main 102 is extended along the outer surfaces of the front wallportion 57 and the left sidewall portion 48 and connected to the DCpower source 9 through the polarity switch-over relay 28. The feederwires 103, the energizing terminal base 98 and the main 102 constitutethe other energizing line 27.

G. Structure of Connection of Carbon Electrode with Feeder Wires (FIG.16)

Each of the feeder wires 93 has a conductor 104 and acorrosion-resistant insulating coating layer 105. A terminal end m ofthe conductor 104 protrudes from the corrosion-resistant insulatingcoating layer 105 of the feeder wire 93. The terminal end m is connectedto a conductive connecting bolt 106. A connecting bore 107 is defined ina corner of the carbon electrode 13 and has a threaded portion n. Theconnecting bolt 106 is threadedly engaged with the threaded portion n.

The connecting bore 107 may be a blind bore, but in the illustratedembodiment, the connecting bore 107 is a through-bore extendingobliquely and vertically. The feeder wire 93 and the connecting bolt 106are inserted into the connecting bore 107 through a lower opened end oof the connecting bore 107. To this end, the connecting bolt 106 has atool, e.g., an engage portion for engagement with a minus screwdriver,namely, an engage groove 108, at an end opposite from an end to whichthe feeder wire 93 is connected.

A seal material 109, such as a silicone, is filled in a void space p ofthe connecting bore 107. The void space p is located between the loweropened end o of the connecting bore 107 and an end face of theconnecting bolt 106 on the side of the engage groove 108. A sealmaterial 109, similar to the above seal material, is also filled in avoid space r of the connecting bore 107. The void space r is locatedbetween an upper opened end g and an end face of the connecting bolt106, from which the feeder wire 93 extends. The void space r surroundsthe insulating coating layer 105 of the feeder wire 93.

The connection of the connecting bolt 106 with the terminal end m of theconductor 104 of the feeder wire 93 is as follows; The connecting bolt106 is formed of titanium which enhances corrosion resistance of theconnecting bolt 106. The connecting bolt 106 has a blind bore 110 whichis open at one end face of the bolt. A hollow tubular member 111 made ofa copper alloy, e.g., brass in the illustrated embodiment, ispress-fitted into the blind bore 110. The terminal end m of theconductor 104 is inserted into the hollow tubular member 111 andconnected thereto through a soldering layer 112. Since titanium is hardto solder, the hollow tubular member 111 made of brass which is easierto solder is used.

A seal member 113, similar to the above-described seal material, isdisposed between one end face of the hollow tubular member 111 and anend face of the insulating coating layer 105 of the feeder wire 93. Theseal member 113 surrounds the conductor 104 protruding from the end faceof the insulating coating layer 105. Thus, the conductor 104, protrudingfrom the hollow tubular member 111 made of brass, and the insulatingcoating layer 105 are made water-tight with respect to the aqueoussolution of NaCl 11.

With the above construction, the carbon electrode 13 and the feeder wire93 are connected within the connecting bore 107 in the carbon electrode13. Hence, only the feeder wire 93 is exposed to the outside, therebyproviding a compact connecting structure.

In addition, the connecting portion between the carbon electrode 13 andthe conductor 104 of the feeder wire 93 is reliably sealed. Hence, theconnecting portion is water-tightly sealed from the aqueous solution ofNaCl 11 which prevents corrosion of the connecting portion.

Since the connecting portion is water-tight as described above, thecarbon electrode 13 can be immersed into the aqueous solution of NaCl11. Thus, the effective volume of the aqueous solution of NaCl 11 isincreased when compared with when the upper portion of the carbonelectrode protrudes from the liquid level, and the connecting portion isdisposed therein.

Moreover, since the connecting bolt 106 is threadedly engaged with theinternal threaded portion n of the carbon electrode 13, close contactbetween the internal threaded portion n and the connecting bolt 106 canbe improved. Thus, the carbon electrode 13 and the feeder wire 93 can bereliably electrically connected to each other.

The connecting bolt 106 and the end of the feeder wire 93 connected tothe connecting bolt 106 are fixed within the connecting bore 107 by theseal material 109. Thus, the mechanical connection between the carbonelectrode 13 and the feeder wire 93 is very strong.

H. Corrosion Test for Test Material (FIGS. 1 to 3, 13, 15 and 17 to 21)

For a corrosion test of the test material 2, a damaged portion 114 isformed by a cutter in the coating film 4 on one flat surface of the testmaterial 2. The damaged portion 114 cuts through the coating film 4 andreaches the steel plate 3, as shown in FIGS. 2 and 3. In this case, thecoating film 4 on the other surface of the test material 2 and thecoating film 4 on the peripheral surfaces function as a mask for thesteel plate 3. A bore 115 in the test material 2 is used for passing ahanging string 25, made of the synthetic resin, therethrough.

The corrosion test of the test material 2 includes a process ofimmersing the test material 2 into the aqueous solution of NaCl 11,allowing a DC current to flow between the steel plate 3 and both carbonelectrodes 13 in the aqueous solution of NaCl 11 and alternatelyswitching over the polarity of the steel plate 3 to positive or negativepolarity.

When the polarity of the steel plate 3 is negative, the coating filmpeeling-off step is performed. During this step, starting at the damagedportion 114 of the coating film, OH ions produced by electrolysis ofwater reduces the adhesion force of the coating film to the steel plate3, thereby promoting the peel-off of and blistering of the coating film.On the other hand, when the polarity of the steel plate 3 is positive,the steel plate corroding step, i.e. the anode oxidation process isperformed. By alternately repeating the peeling-off and anode oxidationof the coating film, the peeling-off of the coating film 4 and thecorrosion of the steel plate 3 starting with the damaged portion 114 canbe promoted. Thus, an overall evaluation of corrosion resistance can beperformed within a short period of time.

During the steel plate corroding step, the amount of steel plate 3corroded is proportional to an amount of coulombs used for energization.However, even in the same amount of coulombs is used, if the coatingfilm peeled-off area of the steel plate 3 is varied, the amount ofcorrosion is varied. Therefore, the amount of coulombs required tocorrode the steel plate 3 is determined based on the coating filmpeeled-off area of the steel plate 3.

Thus, a procedure is used which measures the coating film peeled-offarea of steel plate 3 after the coating film peeling-off step, anddetermines the amount of coulombs used in the steel plate corroding stepin accordance with the coating film peeled-off area of the steel plate3.

FIG. 17 illustrates a corrosion test process. The corrosion test processwill be described specifically with reference to FIG. 17.

(a) First Coating Film Peeling-off Step

At this step, the polarity of both carbon electrodes 13 in the aqueoussolution of NaCl 11 is set at a positive polarity, while the polarity ofthe steel plate 3 of the test material 2 is set at a negative polarityby the polarity switch-over relay 28, as shown in FIG. 17(i). Anelectric current is supplied under a constant voltage from the DC powersource 9 between the carbon electrodes 13 and the steel plate 3 throughthe aqueous solution of NaCl 11.

After a lapse of 5 to 10 minutes from the start of supplying thecurrent, namely, after the current value is stabilized to some extent. avalue I₀ of an electric current flowing in the steel plate 3 is measuredby an ammeter 29.

If the peeling-off of the coating film 4 does not occur within theabove-described time, a peeled-off coating film 4a is produced by asubsequent supplying of electric current, as shown in FIG. 17(ii).

The measurement of the current value I₀ may be carried out before thestart of the first coating film peeling-off step. In this case, thepolarity of the steel plate 3 is set at a negative polarity. If thepolarity of the steel plate 3 is set at a positive polarity, the steelplate 3 is corroded at the damaged portion 114 of the coating film 4 andas a result, the coating film 4 is barely peeled off at a next coatingfilm peeling-off step.

(b) Peeled-off Coating Film Removing Step

The test material 2 is withdrawn out of the aqueous solution of NaCl 11,and the peeled-off coating film 4a is removed from the test material 2using adhesive tape, thereby exposing the coating film-peeled of fsurface 3a in the steel plate 3, as shown in FIG. 17(iii). This removalcan be alternatively carried out by ultra-sonic washing or ahigh-pressure water jet in the aqueous solution of NaCl 11.

(c) Second Coating Film Peeling-off Step

In this step, the polarity of both carbon electrodes 13 in the aqueoussolution of NaCl 11 is set at a positive polarity, while the polarity ofthe steel plate 3 of the test material 2 is set at a negative polarityby the polarity switch-over relay 28, as shown in FIG. 17(iv). Anelectric current is supplied under a constant voltage from the DC powersource 9 between the carbon electrodes 13 and the steel plate 3 throughthe aqueous solution of NaCl 11.

After a lapse of 5 to 10 minutes from the start of supplying thecurrent, namely, after the current value is stabilized to some extent, avalue I₁ of an electric current flowing in the steel plate 3 is measuredby the ammeter 29.

If the peeling-off of the coating film 4 does not occur within theabove-described time, a peeled-off coating film 4a is produced by asubsequent supplying of electric current, as shown in FIG. 17(iv).

(d) Step of Setting Amount of Coulombs in Corrosion of Steel Plate

The current values I₀ and I₁ measured at the first coating filmpeeling-off step (a) and the second coating film peeling-off step (c)are introduced to a calculating unit 116. In this calculating unit 116,a difference ΔI between both current values I₀ and I₁ is firstcalculated. This difference ΔI is substantially proportional to thecoating film peeled-off area of the steel plate 3. Hence, themeasurement of the coating film peeled-off area is replaced by thecalculation of the difference ΔI. Then, an amount of coulombs,corresponding to the difference ΔI, is determined in terms of anenergization time T under the constant voltage. This amount of coulombscan be determined by measuring a variation in voltage under a constantcurrent, or by simultaneously measuring a current and a voltage.

(e) First Steel Plate Corroding Step

At this step, as shown in FIG. 17(v), the peeled-off coating film 4aproduced at the second coating film peeling-off step (c) is not removed,and the polarity of the carbon electrodes 13 in the aqueous solution ofNaCl 11 is set at a negative polarity, while the polarity of the steelplate 3 of the test material 2 is set at a positive polarity by thepolarity switch-over relay 28. An electric current is supplied under aconstant voltage from the DC power source 9 between the carbonelectrodes 13 and the steel plate 3 through the aqueous solution of NaCl11. The amount of time for supplying the current is the energizationtime T determined at the step (d) for setting the amount of coulombs.

Thus, a recess 117 is formed in the coating film peeled-off surface 3aof the steel plate 3 by the corrosion (anode oxidization), and acorrosion product 118 is accumulated within the recess 117.

The first steel plate corroding step must be carried out without removalof the peeled-off coating film 4a produced at the second coating filmpeeling-off step (c) in FIG. 17(iv). If the peeled-off coating film 4ais removed, the amount of coulombs determined at the stop (d) and thecoating film peeled-off area of the steel plate 3 are unequal to eachother. In addition, if the peeled-off coating film 4a is not removed,the coating film peeled-off area of the steel plate 3 in this corrodingstep is hardly different from the coating film peeled-off area of thesteel plate 3 produced at the peeling-off coating film removing step (b)in FIG. 17(iii).

(f) Step of Removing Peeled-off Coating Film and Corrosion Product

The test material 2 is withdrawn out of the aqueous solution of NaCl 11,and the peeled-off coating film 4a and the corrosion product 118 areremoved from the test material 2 using adhesive tape, thereby exposingthe coating film peeled-off surface 3a and the recess 117 in the steelplate 3, as shown in FIG. 17(vi). This removal can be carried outalternatively by ultrasonic washing or a high-pressure water Jet in theaqueous solution of NaCl 11.

Thereafter, if required, a plurality of cycles, each including stepsfrom the second coating film peeling-off step to the peeled-off coatingfilm/corrosion product removing step, may be repetitively carried out.In this case, the difference ΔI is calculated, for example, from acurrent value I₁ measured at the second coating film peeling-off step ina first cycle and a current value I₂ measured at the third coating filmpeeling-off step in a second cycle.

If the coating film peeling-off step is carried out subsequent to thesteel plate corroding step, the peeling-off of the coating film 4 isobstructed by the corrosion product 118. Hence, it is necessary tointerpose the peeled-off coating film/corrosion product removing stepbetween both the coating film peeling-off step and the steel platecorroding step.

Particular examples will be described below.

I. Coating film Peeling-off Test

A coating film peeling-off test, which will be described below, wascarried out to examine the relationship between the applied voltage andthe degree of peeling-off of the coating film 4.

(1) Conditions for Test Material 2

Steel plate:

width: 70 mm; length: 150 mm; thickness 1.017 mm Coating film:

A pre-treating agent available under a trade name of SD2800 from NipponPaint is used; a coating method: an cationic electrostatic coating; filmthickness: 20 to 25 μm; a damaged portion is formed into a length of 50mm using a cutter.

In addition, another test material 2 was made under the same conditions,except that the pre-treatment agent was not used.

As shown in FIG. 18, one end of the string 25, made of the syntheticresin, was tied in the bore 115 in the test material 2, and a loop h wasformed at the other end of the string 25. The conductor 104, protrudingfrom the corrosion resistant insulating coating layer 105 of the feederwire 103, was soldered to the steel plate 3 on the opposite surface ofthe test material 2 from the surface having the damaged portion 114provided thereon. Exposed portions of the steel plate 3 in the bore 115and the soldered zone of the test material 2 and the conductor 104 arecovered by a seal member 119. A bolt insertion bore 121 in a terminal120, connected to the other end of the feeder wire 103, was aligned withthe connecting bore 101 in the energizing terminal base 98. A bolt 122was threadedly inserted into the connecting bore 101 through the boltinsertion bore 121. This caused the steel plate 3 and the DC powersource 9 to be electrically connected to each other through the polarityswitch-over relay 28. The test material 2 was immersed into the aqueoussolution of NaCl 11 by hanging it from the support bar 24 through theloop h of the string 25 made of the synthetic resin.

(2) The concentration of the aqueous solution of NaCl 11 was set at 3%,and the temperature of the aqueous solution of NaCl 11 was set at 40° C.The polarity of the steel plate 3 was set at a negative polarity, whilethe polarity of the carbon electrode 13 was set at a positive polarity.The test time was set at 2 hours. The applied voltage was varied in arange of 0 to 20 V. Under such conditions, the coating film peeling-offtest for the test material 2 was carried out.

(3) Test Result

FIG. 19 is a graph illustrating the relationship between the appliedvoltage and the width s of the coating film peeled off from the damagedportion 114 (see FIG. 17 (iii)). As apparent from FIG. 19, thepeeling-off of the coating film 4 is started at the applied voltage ofabout 2.5 V, whether the pre-treatment is carried out or not. To performthe peeling-off of the coating film with stability, it is preferred thatthe applied voltage is set at about 5.5 V or more for the test material2 subjected to the pretreatment and at about 8 V or more for the testmaterial 2 not subjected to the pretreatment.

At the same applied voltage the amount of coating film peeled off issmaller in the test material 2 subjected to the pretreatment than in thetest material 2 not subjected to the pretreatment. As shown from this,pretreatment is preferably carried out in order to enhance thedurability of the coating film 4.

II. Corrosion Resistance Test

(1) Conditions for the test material 2 in the corrosion resistance testare identical to those described in the item I for the coating filmpeeling-off test.

(2) Steps and conditions for the steps in a particular example are asshown in Table 1. In this case, the concentration of the aqueoussolution of NaCl was set at 3%, and the temperature of the aqueoussolution of NaCl was set at 45° C.

                  TABLE I                                                         ______________________________________                                                               Current          Energizing                            Cycle                                                                              Step      Voltage Value   Difference ΔI                                                                    time                                  ______________________________________                                             first     16 V    I.sub.0 = 1.9 A                                                                       --       4 hours                                    peeling-off                                                              1    second    16 V    I.sub.1 = 14.9 A                                                                      I.sub.1 - I.sub.0                                                                      4 hours                                    peeling-off                                                                   first steel                                                                             10 V    --      --       T = 1810                                   plate                              seconds                                    corrosion                                                                2    third     16 V    I.sub.2 = 18.3 A                                                                      I.sub.2 - I.sub.1                                                                      4 hours                                    peeling-off                                                                   second    10 V    --      --       T = 1984                                   steel plate                        seconds                                    corrosion                                                                3    fourth    16 V    I.sub.3 = 19.6 A                                                                      I.sub.3 - I.sub.2                                                                      4 hours                                    coating film                                                                  peeling-off                                                                   third steel                                                                             10 V    --      --       T = 1986                                   plate                              seconds                                    corrosion                                                                4    fifth     16 V    I.sub.4 = 19.4 A                                                                      I.sub.4 - I.sub.3                                                                      4 hours                                    coating film                                                                  peeling-off                                                                   fourth steel                                                                            10 V    --      --       T = 1472                                   plate                              seconds                                    corrosion                                                                ______________________________________                                    

(3) A cycle corrosion test (CCT) enabling the deterioration of thecoating film 4 and the corrosion of the steel plate 3 to besimultaneously estimated was carried out as a comparative example, usinga test material 2 subjected to a pretreatment similar to theabove-described pretreatment and a test material 2 not subjected to thepretreatment. Conditions for this test are as follows: a step forcarrying out a spraying of salt water for 2 hours, a wetting for 2 hoursand a drying for 4 hours was repeated three times. This was defined asone cycle. Therefore, the time required for one cycle is 24 hours.

(4) Result of Test

FIG. 20 is a graph illustrating the relationship between the cycle andthe width s (see FIG. 17 (iii)) of the coating film peeled off from thedamaged portion 114 when 20, 40, 60 and 80 cycles in the comparativeexample correspond to 1, 2, 3 and 4 cycles in the particular example. Asapparent from FIG. 20, the 1 cycle in the particular examplesubstantially compares with 20 cycles in the comparative example in theabove-described width s of coating film peeled off.

Table 2 shows the relationship between the cycle and the maximumdecrement in plate thickness in the particular example using the testmaterial 2 subjected to the pretreatment.

                  TABLE 2                                                         ______________________________________                                                   Maximum decrement in                                               Cycle      plate thickness (mm)                                               ______________________________________                                        1          0.146                                                              2          0.347                                                              3          0.643                                                              4          0.968                                                              ______________________________________                                    

FIG. 21 is a graph illustrating the relationship between the cyclesimilar to the above-described cycle and the maximum decrement in platethickness. Even in the comparative example, the test material 2subjected to the pretreatment was used. As apparent from FIG. 21, the 1cycle in the particular example substantially compares with 20 cycles inthe comparative example even in the above-described maximum decrement inplate thickness.

It is apparent from this result that in the particular example, thepeeling-off of the coating film 4 and the corrosion of the steel plate3, i.e., the metal blank, can be promoted, and the overall evaluation ofthe corrosion resistance can be performed in a short time.

When only the coating film peeling-off test for the film 4 is carriedout, the polarity switch-over relay 28 is switched over, so that thepolarity of the steel plate 3 is negatively polarized as describedabove. In this case, the coating film 4 is provided only on one surfaceof the steel plate 3 because the steel plate corroding step is notincluded. Hence, it is unnecessary to mask the other surface of thesteel plate 3.

I. Determining Device for Determining Timing of Replacement of CarbonElectrode (FIGS. 4 to 6 and 22 to 24)

Carbon particles are dropped by the carbon electrode 13 as a result ofuse of the carbon electrode 13 for a long time and the conductive areavaries. In order to replace the carbon electrode 13 by a new carbonelectrode 13, if it reaches the end of its service life, a determiningdevice 123 is mounted in the electrolytic test machine 1. The device 123is incorporated in the computer programmed control unit 10.

FIG. 22 is a block diagram of the determining device 123, and FIG. 23 isa flow chart illustrating the operation of the device 123. The term "settest conditions" in FIG. 23 means that any one of the followingconditions are selected: a) the corrosion test including the coatingfilm peeling step and the steel plate corroding step is to be carriedout, b) the coating film peeling-off test is to be carried out and c)the test is to be finished. Conditions selected are then input.

Referring to FIG. 22, the determining device 123 includes a life memorymeans 124 for storing the service life of the carbon electrode 13 in theform of an effective current amount C₁ which is a product I₁ ·T₁ of acertain current I₁ flowing in the carbon electrode 13 and a total testtime T₁ capable of being used when the current I₁ continues to flow. Acurrent measuring means (ammeter) 29 measures a current 12 flowing inthe carbon electrode 13, during a test. A time measuring means 125measures a test time T₂. A first calculating means 132₁ calculates aused current amount C₂ which is a product I₂ ·T₂ of the current I₂ andthe test time T₂. An integrating means 126 integrates the used currentamounts C₂ to calculate an integration used current amount C₃ from thestart of the use of the carbon electrode 13. A memory means 127 storesthe integration used current amount C₃. A control means 128 compares theeffective current amount C₁ with the integration used current amount C₃at the start of the test and to transmit an electrode replacing signal,when C₁ <C₃.

With such an arrangement, as the carbon electrode 13, which is aconsumable electrode, reaches the end of its service life, thereplacement time of the carbon electrode 13 can be automaticallydetected.

In this case, even if the relationship between the effective currentamount C₁ and the integration used current amount C₃ becomes C₁ <C₃, thetest is continued. This is permitted by depending on a margin of theeffective current amount C₁ corresponding to several runs of the test.

The determining device 123 includes a) a message indicating means 129for informing a testing operator of reaching the electrode replacingtiming, based on the electrode replacing signal from the control means128, and b) a prohibiting means 130 for prohibiting the supplying ofcurrent to the carbon electrode 13.

As best shown in FIGS. 4 to 6 and 24, a message on the messageindicating means 129 is displayed by characters on a liquid crystaldisplay plate 131 mounted on the upper surface of the left cover 52which covers the control section C. The prohibiting means 130 isoperated to maintain the DC power source 9 in its OFF state. Thus, thetesting operator can reliably know the replacement time of the carbonelectrode 13.

As shown in FIG. 23, the determining device 123 is constructed, so thatthe device 123 will not operate after replacing the electrode 13 unlessthe integration used current amount C₃ stored in the memory means 127 isreset to 0.

If the effective current amount C₁ and the integration used currentamount C₃ are in a relation of C₁ ≧C₃ prior to starting the test, thetest is started, and the calculation and the integration of the usedcurrent amount C₂ and the like are carried out.

The determining device 123 includes a second calculating means 132₂ forsubtracting the integration used current amount C₃ from the effectivecurrent amount C₁ in the carbon electrode 13 to determine a remainingeffective current amount C₄, and a remaining effective currentindicating means 133 for indicating the remaining effective currentamount C₄.

The second calculating means 1322 calculates the remaining effectivecurrent amount C₄ according to C₄ (%)={1-(C₃ /C₁)}×100. The remainingeffective current amount C₄ indicated by the remaining effective currentamount indicating means 133 is indicated by a bar graph on the liquidcrystal display plate 131, so that the remaining effective currentamount C₄ is gradually decreased, as shown in FIG. 24. Thus, it ispossible for the testing operator to easily know the remaining servicelife of the carbon electrode 13 and the variations therein.

When the effective current amount C₁ and the integration used currentamount C₃ are in a relation of C₁ ≦C₃, the effective current amount C₄is displayed as being C₄ =0%.

J. Structure of Sealing of the Opening in the Electrolytic Cell (FIGS. 6to 10, 13 and 25 to 27)

As shown in FIG. 10, the heights of the front and rear wall portions 57and 71 in the peripheral wall 47 of the electrolytic cell 12 are lowerthan heights of the left and right sidewall portions 48 and 49. Part ofeach of the left and right sidewall portions 48 and 49, which protrudesfrom the front and rear wall portions 57 and 71, has a vertical frontedge 134, a forward declined upper edge 135, a horizontal upper edge136, a rearward declined upper edge 137 and a vertical rear edge 138. Aseal member 139, made of a rubber, is mounted on the upper edges of thefront and rear wall portions 57 and 71 and all the edges 134 to 138 ofthe left and right sidewall portions 48 and 49, i.e., an entireperipheral edge of the upward opening 19.

As best shown in FIG. 25, the central cover section 51 is comprised of afront wall 140, a rear wall 141 and an upper wall 142 which connects thefront and rear walls 140 and 141 to each other. The central coversection 51 is placed over the electrolytic cell 12 from above theelectrolytic cell 12. Thus, the front, upper and rear portions of theelectrolytic cell 12 are covered with the central cover section 51. Asshown in FIGS. 8, 9 and 25, inward-turned projecting pieces 143 areprovided on right and left ends of lower portions of inner surfaces ofthe front and rear walls 140 and 141. The projecting pieces 143 at theright end are detachably mounted to front and rear angle members 144extending vertically to form the frame 90 of the machine base 44. Theprojecting pieces 143 at the left end are detachably mounted to frontand rear angle members 145 extending vertically of the machine base 44.

As best shown in FIGS. 6, 10 and 25, the upper wall 142 has an outerperipheral frame-like section 146, and a recess 147 surrounded by theouter peripheral frame-like section 146. The recess 147 is comprised ofa relatively large and shallow recess portion 148 located on a frontside, and a relatively small and deep recess portion 149 located on arear side. The quadrilateral opening 21 for placing the test material 2into and for removing the test material 2 out of the electrolytic cell12 is provided in a bottom wall t of the shallow recess portion 148.

Each of left and right portions 150 and 151 of the outer peripheralframe-like section 146 has a shape extending along the forward-declinededge 134, the horizontal upper edge 136 and the rearward-declined upperedge 137 in the left and right sidewall portions 48 and 49 of theelectrolytic cell 12, as shown in FIG. 10. In addition, each of left andright portions t₁ and t₂ of the bottom wall of the shallow recessportion 148 has a shape extending along portions of the forward-declinedupper edge 135 and the horizontal upper edge 136.

As best shown in FIGS. 7, 10, 25 and 26, left and right sidewalls u₁ andu₂ of the recess 147 are fitted between the left and right sidewallportions 48 and 49 of the electrolytic cell 12. Thus, lower surfaces ofthe left and right portions 150 and 151 of the outer peripheralframe-like section 146 are brought into close contact with the uppersurface of the seal member 139 at portions of the forward-declined upperedge 135, the horizontal upper edge 136 and the rearward-declined upperedge 137 of the left and right sidewalls 48 and 49. In addition, outersurface of the left and right sidewalls u₁ and u₂ of the recess 147 arebrought into close contact with the inner surface of the seal member 139at the vertical front edge 134, the forward-declined upper edge 135, thehorizontal upper edge 136, the rearward-declined upper edge 137 and thevertical rear edge 138 of the left and right sidewall portions 48 and49.

As best shown in FIGS. 7, 10, 13 and 27, a lower surface of a frontportion t₃ of the bottom wall of the shallow recess portion 148 isbrought into close contact with the upper surface of the seal member 139at the front wall portion 57 of the electrolytic cell 12. A lowersurface of a bottom wall v of the deep recess portion 149 is broughtinto close contact with the upper surface of the seal member 139 at therear wall portion 71 of the electrolytic cell 12.

In this way, when the central cover section 51 is placed over theelectrolytic cell 12 from above the electrolytic cell 12 and mounted tothe machine base 44, the opening. 19 in the electrolytic cell 12 can bereliably sealed.

K. Structure for Opening and Closing Lid and Structure for CollectingWater Drops Deposited on Inner Surface of Lid (FIGS. 4 to 7, 9, 13, 14and 25 to 28)

As shown in FIGS. 4, 6, 26 and 27, an annular seal member 152 is mountedto that entire peripheral edge of the upper wall of the central coversection 51 which defines the upward opening 21. The annular seal member152 includes an annular lip 152a which protrudes from an upper surfaceof the annular seal member 152 and surrounds the opening 21. Thus, anannular tub 153 is formed by cooperation of the annular seal member 152,the shallow recess portion 148 and the deep recess portion 149 with oneanother. The tub 153 is located outside the annular seal member 152 tosurround the annular seal member 152. Left and right grooves 154 and 155in the annular tub 153 are forward declined. A front groove 156 in theannular tub 153 assumes a V-shape. As best shown in FIGS. 6, 14 and 27,drainage ports 157 and 158 are opened in right ends of bottoms of thefront groove 156 and the rear deep recess portion 149. The drainageports 157 and 158 are connected to a downstream portion of the drainagepipe line 18 from the manual cock 32 through a tube 159.

As best shown in FIGS. 4, 5, 13 and 27, the lid 22 for opening andclosing the opening 21 includes a transparent synthetic resin plate 160located in a front side which forms a main body of the lid 22. A steelplate 161 made of a stainless steel is mated to a rear edge of the plate160. As best shown in FIGS. 6 and 13, when the opening 21 has beenclosed, the transparent synthetic resin plate 160 covers thesubstantially entire shallow recess portion 148, with its inner surfaceput in close contact with the annular lip 152a of the annular sealmember 152. The steel plate 161 covers the substantially entire deeprecess portion 149, with its rear edge 161a located in the vicinity ofan opening of the deep recess portion 149. Namely, the substantiallyentire annular tub 153 is covered with the lid 22.

A pair of brackets 162, made of a stainless steel, is disposed at apredetermined distance on an inner surface of the steel plate 161. Apair of reinforcing rib members 163 is disposed on an outer surface ofthe steel plate 161. The pair of brackets and the pair of reinforcingrib members 163 are coupled to each other by a plurality of bolts withthe steel plate 161 interposed therebetween. Protrusions 163a of thereinforcing rib members 163 are disposed on an outer surface of a rearportion of the transparent synthetic resin plate 160 to project forwardsfrom the steel plate 161. The protrusions 163a are coupled to rearportions of a pair of reinforcing rib members 165 by a plurality ofbolts 166 with the transparent synthetic resin plate 160 interposedtherebetween. The pair of reinforcing rib members 165 are made of asynthetic resin and are disposed on an inner surface of the main plate160. A front portion of each of the reinforcing rib members 165 isbonded to the transparent synthetic resin plate 160.

As best shown in FIGS. 6, 7 and 9, a support shaft 167 for the lid 22extends laterally in a substantially central area of the deep recessportion 149 in such a manner that its opposite ends are passed throughthe left and right sidewalls u₁ and u₂ of the recess 147 and the leftand right sidewall portions 48 and 49 of the electrolytic cell 12. Thesupport shaft 167 is turnably supported on bearings 169 mounted on outersurfaces of reinforcing plates 168 made of a steel and mounted on theouter surfaces of the left and right sidewalls 48 and 49. The supportshaft 167 is passed through the brackets 162 of the lid 22 and shorttubes 170 fixed to the brackets 162, and is coupled in arotation-prevented manner to the short tube 170.

As best shown in FIGS. 7, 9 and 28, a right end of the support shaft 167protruding from the right sidewall portion 49 of the electrolytic cell12 is passed through an upper end of a link 171 and a short tube 172fixed to the link 171. The right end of the support shaft 167 is coupledto the short tube 172 in a rotation-prevented manner. The link 171 ispivotally connected at its lower end, through a connecting pin 174, to apiston rod 173 of the electric power cylinder 23 which is disposed belowthe link 171.

A cylinder body 175 of the power cylinder 23 is pivotally connected atits lower end to a bifurcated support member 176 of the machine base 44through a connecting shaft 177. The support member 176 is fixed to amounting base 179 which is supported by the lower angle member 91 of theframe 90 and a support pillar 178. The power cylinder 23 includes anelectric motor 180 integral with the cylinder body 175.

On the outer surface of the right sidewall portion 49 of theelectrolytic cell 12, a guide plate 181 for the link is disposed in ansuperposed relation to the reinforcing plate 168. The guide plate 181has L-shaped legs 183 at upper and lower edges of a flat plate portion182 thereof. The legs 183 are mounted to the right sidewall portion 49through the reinforcing plate 168. The flat plate portion 182 has anotch 184 for avoiding interference with the support shaft 167, and anarcuate guide bore 186 in which a guide pin 185 projectingly is slidablyfitted and which extends vertically. Limit switches 187 and 188 aremounted to an inner surface of the flat plate portion 182 in thevicinity of upper and lower ends of the guide bore 186 and are operatedby the guide pin 185. The lower limit switch 188 determines a closedposition of the lid 22, as shown in FIG. 9, and the upper limit switch187 determines an opened position of the lid 22, as shown in FIG. 28.When the opening 21 is opened, one end of the lid 22 on the side of itsrotational center, e.g., the rear edge 161a of the steel plate 161 inthe illustrated embodiment, is disposed within the deep recess portion149 of the annular tub 153, as best shown in FIG. 27.

In the corrosion test, the temperature of the aqueous solution of NaCl11 rises to about 40° C. as described above. Hence, many waterdrops arelikely to be deposited onto the inner surface of the transparentsynthetic resin plate 160 of the lid 22 which closes the opening 21.

With the above construction, many waterdrops deposited on the innersurface of the transparent synthetic resin plate 160 are displaced uponopening of the lid 22, and dropped from the rear edge 161a via the steelplate 161 into and collected in the deep recess portion 149 of theannular tub 153. Waterdrops deposited on the annular seal member 152 anddropped outside the seal member 152 are likewise collected into theannular tub 153. The water collected in the above manner is dischargedthrough the tube 159 into the drainage pipe line 18.

As shown in FIGS. 4, 10, 13, 25 and 27, an L-shaped plate 189 is mountedto a lower portion of the front wall 149a defining the deep recessportion 149 in the central cover section 51. A fine groove 190 isdefined by cooperation of the L-shaped plate 189 and the front wall 149awith each other. An upper folded edge 191a of a cover member 191,covering the heater chamber 68, is engaged in the fine groove 190. Alower portion 191b of the cover member 191 is fitted into a notch-likerecess 67a in a rear surface of the upper portion of the partition plate67 defining the heater chamber 68, as shown in FIGS. 11 and 13.

L. Structure of Coupling of Central Cover Section and Left and RightCover Sections (FIGS. 6 to 8, 25 and 26)

The structure of coupling the central cover section 51 covering thefront, upper and rear portions of the electrolytic cell 12 and the leftcover section 52 covering the control section C, adjacent the centralcover section 51, is constructed in the following manner: As best shownin FIGS. 25 and 26, a recessed groove 192 is defined in an edge of thecentral cover section 51, which is adjacent the left cover section 52,continuously over the entire periphery thereof, so that the groove 192is opened and forms a J or U shape. A projection 193 is formed on anedge of the left cover section 52, which is adjacent the central coversection 51, continuously over the entire periphery thereof, so that itis folded inward or downward into an L shape.

When the central cover section 51 has been fixed to the machine base 44,the left cover section 52 is coupled to the central cover section 51 bybringing the lower end of the L-shape portion of the projection 193 ofthe left cover section 52 into engagement with the J or U shaped portionof the recessed groove 192 in the central cover section 51 to lower theleft cover section 52, and then bringing the upper portion of theprojection 193 into engagement with the upper portion of the recessedgroove 192. The structure of coupling of the central cover section 51and the right cover section 53 is the same as the above structure.

With such a construction, even if the left and right cover sections 52and 53 have water poured upon them, the water is prevented from enteringinto the control section C and the mechanical section M.

The water, entering the coupled portions of the central cover section 51and the left and right cover sections 52 and 53, is received into therecess 192 and discharged downwards.

During maintenance of the electrolytic cell 12, the mechanical section Mand the control section C, the left and right cover sections 52 and 53can be easily lifted and removed from the central cover section 51.Similarly, the left and right cover sections 52 and 53 are easilyrecoupled to each other. In addition, removing and attaching operationsare not required, because no seal member is used at each of the coupledportions.

Thus, maintenance of the electrolytic cell 12, the mechanical section Mand the control section C, is improved over the prior art.

M. Chlorine Gas Treating Device

(1) Entire Structure and Function thereof (FIGS. 4, 7 to 11, 13, 14 and29 to 34)

At the coating film peeling-off step in the corrosion test, a chlorinegas is generated on the side of the carbon electrodes 13 with theelectrolysis of the aqueous solution of NaCl 11 due the polarity of thecarbon electrodes 13 being set at a positive polarity.

The chlorine gas treating device 6 is mounted in the electrolytic testmachine 1 to purify the chlorine gas. The treating device 6 collects thechlorine gas generated around the carbon electrodes 13 in response tothe electrolysis of the aqueous solution of NaCl 11, together with apart of the aqueous solution of NaCl 11, adsorbs the chlorine gas,decomposes NaClO which is a product of reaction of the NaOH and thechlorine gas produced by the electrolysis of the aqueous solution ofNaCl 11, thereby producing NaCl, returns the NaCl to the electrolyticcell 12 and decomposes HClO which is a similar reaction product.

The chlorine gas treating device 6 will be described more specificallybelow. As shown in FIGS. 4, 7, 8, 10, 11 and 13, a chlorine gascollecting hood 194 is placed on the partition plate 54 and the divisionplate 56 in the left electrode chamber 55. A mounting plate 195,integral with the hood 194, is screwed to the left sidewall portion 48of the electrolytic cell 12. As best shown in FIGS. 7 and 11, the hood194 covers the entire upper portion of the electrode 13 and closes theupward opening 55a in the electrode chamber 55. The hood 194 includes abox-like hood body 196 placed on the partition plate 54 and the divisionplate 56, and a roof-like portion 197, integral with the hood body 196,and assuming an angle shape in cross section. A lower surface of theroof-like portion 197, namely, a lower ridgeline 199 is inclined at anangle α≧1 degree, so that its rear end, which is a first end, is locatedat a higher elevation than its front end which is the other or secondend. A through-hole 200 is defined in the rear end of the roof-likeportion 197 for venting air within the electrode chamber 55 at the startof supplying water into the electrolytic cell 12.

A sucking side of the treating pipe line 33 is passed through the bottomwall 83 of the electrolytic cell 12, and a sucking pipe 201, which is aterminal end thereof, rises within the electrode chamber 55 which is anelectrode immersion zone. The sucking pipe 201 has a suction port 202which is disposed in proximity to the portion of the ridgeline 199 ofthe roof-like portion 197 which is located at the higher elevation. Thesuction port 202 is inclined forwards and toward the ridgeline 199 inorder to smoothly suck in the chlorine gas as best shown in FIGS. 7, 11and 29, a pair of baffles 203 are provided on the hood 194 over opposedinner surfaces of the hood body 196 and the lower surface of theroof-like portion 197 to lie on opposite sides of the suction port 202.The baffles 203 act to prevent the chlorine gas from escaping from thesuction port 202 and flowing toward the air venting through-hole 200.

The suction pipe 201 extends along the rear surface of the protrudingplate 61 which is located on the left sidewall portion 48 of theelectrolytic cell 12. The suction pipe 201 is fitted into a through-hole205 in an annular member 204 which is projectingly provided on an upperportion of the rear surface of the protruding plate 61, and is held in astationary state in the electrolytic cell 12

A chlorine gas collecting hood 194 and a suction pipe 201 similar tothose described above are also in the right electrode chamber 55.Therefore, in the right electrode chamber 55, like reference charactersare affixed to portions or components similar to those of the leftelectrode chamber 55.

As best shown in FIGS. 7, 8 and 14, the treating pipe line 33, includingthe two suction pipes 201, extends from the inside of the machine base44 via mechanical section M along the outer surface of the rear wallportion 71 of the electrolytic cell 12. The line 33 is then bifurcatedand enters two discharge ports 206 located in the rear wall portion 71of the electrolytic cell 12. The discharge ports 206 open into portionsof the heater chamber 68 in which the aqueous solution of NaCl 11 isstored.

As best shown in FIGS. 9 and 14, the suction pump 34 is disposed in thetreating pipe line 33 in the mechanical section M. On the side of theoutlet of the suction pump 34 in the treating pipe line 33, the chlorinegas purifying device 35 is disposed upstream, and the flow rate sensor36 for detecting an abnormality of the treating system is disposeddownstream. The suction pump 34 is mounted to a support member 207 onthe machine base 44, and the chlorine gas purifying device 35 is mountedon a support 208 on the machine base 44. The suction pump 34 has asuction port 209 in its lower end face, and a discharge port 210 in alower end of its outer peripheral surface.

A drainage pipe 211 diverges from the treating pipe line 33 at alocation adjacent the suction side of the suction pump 34. The drainagepipe 211 has a manual cock 212 at its intermediate portion and isconnected to the drainage pipe line 18 at a location downstream from themanual cock 32. The drainage pipe 211 is located at a level which islower than the suction pump 34 and the chlorine gas purifying device 35.Thus, it is possible to withdraw water from the suction pump 34 and thechlorine gas purifying device 35.

The chlorine gas purifying device 35 includes a filter and a catalysttherein. The catalyst adsorbs the chlorine gas and decomposes NaClO andHClO which are, reaction products. The NaClO and HClO whiten the coatingfilm 4 by their bleaching effects, so that the appearance of the coatingfilm 4 is significantly different from a corroded state in a naturalenvironment. Therefore, it is necessary to decompose NaClO and HClO

If the chlorine gas treating device is constructed in the above manner,the chlorine gas generated around the carbon electrodes 13 immersed inthe aqueous solution of NaCl 11 in the electrolytic cell 12 isimmediately collected along with the aqueous solution of NaCl 11,released from the aqueous solution of NaCl 11, then purified by thechlorine gas purifying device 35. Thereafter, the aqueous solution ofNaCl 11 is returned to the electrolytic cell 12.

In this case, the foamy chlorine gas generated in the vicinity of eachof the carbon electrodes 13 is floated up in the aqueous solution ofNaCl 11 and smoothly introduced in the form of a foam to the suctionport 202 by a guiding effect of the chlorine gas collecting hood 194. Inaddition, the chlorine gas is effectively sucked in through the suctionport 202 into the treating pipe line 33 by the baffles 203 forpreventing the gas from escaping from the suction port. The generatedchlorine gas cannot be accumulated within the hood 194 by virtue of theinclination of the lower surface of the hood 194. Furthermore, theaccumulated chlorine gas cannot be vented and hence, the suction pump 34cannot intake air.

Thus, the diffusion of the chlorine gas into the aqueous solution ofNaCl within the electrolytic cell 12 is inhibited. Therefore, it ispossible to inhibit the production of NaClO and HClO in the aqueoussolution of NaCl 11 and the dissolution of the chlorine gas into theaqueous solution of NaCl 11 is inhibited to the maximum.

FIG. 30 illustrates the relationship between the test time and theeffective concentration of chlorine with regard to activated carbon,ruthenium carbon (a mixture of ruthenium and carbon) and granular nickelused as a catalyst in the chlorine gas purifying device 35. In FIG. 30,the term "effective concentration of chlorine" indicates a determinedamount of chlorine gas dissolved in the aqueous solution of NaCl 11 (seeJapanese Industrial Standard JIS K1425). In measuring the effectiveamount of chlorine, a procedure was employed which involves continuouslysupplying an electric current at 50 A for 20 hours while maintaining thetemperature of the aqueous solution of NaCl 11 at 45° C., sampling 200cc of the aqueous solution of NaCl 11, throwing the catalyst into thesampled aqueous solution of NaCl 11 the temperature of which ismaintained at 45° C., and determining the effective concentration ofchlorine after a lapse of a predetermined time. As apparent from FIG.30, the activated carbon and the ruthenium carbon, having an excellenteffective chlorine decomposing capability, are effective as the catalystused in the chlorine gas purifying device 35.

FIG. 31 illustrates the relationship between the test time and theeffective concentration of chlorine when activated carbon was used asthe catalyst. Conditions for the test are such that an electric currentof 50 A is supplied continuously, and the temperature of the aqueoussolution of NaCl 11 is 45° C. As apparent from FIG. 31, if theabove-described treating device 6 is used, and activated carbon is usedas the catalyst, the effective concentration of chlorine can bemaintained at an extremely low value such as about 0.003% or lower, evenafter the test time exceeds 20 hours.

FIG. 32 illustrates the test time and the effective concentration ofchlorine when electric current of 20 A was continuously supplied at atemperature of the aqueous solution of NaCl 11 equal to 45° C. In thiscase, the effective concentration of chlorine can be maintained at about0.004% or lower, even after the test time exceeds 100 hours.

As a result of the various tests, it was confirmed that if the effectiveconcentration of chlorine is equal to or lower than 0.005%, thewhitening of the coating film 4 does not occur.

Na⁺ ion and OH⁻ ion are contained in the aqueous solution of NaCl.Therefore, if the chlorine gas is collected along with the aqueoussolution of NaCl, chemical reactions represented by the followingchemical formulae occur between NaOH and the chlorine gas, therebycausing a portion of chlorine gas to be regenerated as NaCl. Theregenerated NaCl is returned into the electrolytic cell 12 to contributeto the suppression of a variation in concentration of NaCl in theaqueous solution of NaCl 11. ##EQU1##

The chlorine gas decomposing reaction as described above is promotedmore, when the amount of NaOH is large.

Therefore, attention of the present inventors was drawn to the fact thatNaOH attendant on the electrolysis of the aqueous solution of NaCl 11 isproduced in the test material immersion zone within the electrolyticcell 12 due to the polarity of the test material 2 being set at acathode. The electrolytic test machine 1 is arranged so that NaOHproduced in the test material immersion zone can be introduced to bothelectrode chambers 55.

HClO and NaClO, produced by both the above-described chemical reactionsas well as HClO and NaClO produced within the electrolytic cell 12during the test and collected along with the chlorine gas, aredecomposed mainly by chemical reactions with activated carbon (includingruthenium carbon) C of the chlorine gas purifying member 35. Thesereactions are represented by the following reaction formulae: ##EQU2##

The regenerated NaCl is likewise returned into the electrolytic cell 12to contribute to the suppression of a variation in concentration of NaClin the aqueous solution of NaCl 11. The produced HCl is returned intothe aqueous solution of NaCl 11 and neutralized by a reaction with NaOHproduced by the electrolysis. This also regenerates NaCl.

As can be seen from the above-described chemical reaction formulae,activated carbon C is wasted in the form of CO₂. The activated carbon iswasted because it decomposes NaClO and HClO. Therefore, if NaClO and thelike are previously decomposed in another method to decrease the amountof NaClO and the like which are to be loaded to the activated carbon,the load of the activated carbon can be alleviated to provide aprolongated life for the activated carbon.

Since the electrolytic testing machine 1 is arranged so that NaOH,produced in the test material immersion zone, can be introduced intoboth electrode chambers 55, a chemical reaction which is represented bythe following reaction formula:

    2HClO+NaClO+2NaOH→NaClO.sub.3 +2NaCl+2H.sub.2 O

can be produced to eliminate predetermined amounts of HClO and NaClO,thereby alleviating the load of the activated carbon.

FIG. 33 shows an NaOH introducing device 401 mounted in the electrolyticcell 12 for introducing NaOH produced in a test material immersion zone400 within the electrolytic cell 12 to both electrode chambers 55. TheNaOH introducing device 401 includes an introducing pipe line 402, and asuction pump 403 disposed in the introducing pipe line 402. Theintroducing pipe line 402 has an inlet 404 disposed in the test materialimmersion zone 400, and two outlets 405 disposed in both electrodechambers 55, respectively.

FIG. 34 illustrates the relationship between the testing time and theconcentration of chlorine gas above a liquid level f within theelectrolytic cell 12, when the NaOH introducing device 401 has beenoperated and when the device 401 has not been operated. Testingconditions are as follows: Electric current of 20 A is continuouslysupplied; the amount of activated carbon is 550 g; and the temperatureof the aqueous solution of NaCl 11 is 45° C. As can be seen from FIG.34, if about 25 hours lapse from the start of the test undernon-operation of the device. 401, the concentration of chlorine gas issuddenly increased. This is due to wasting of the activated carbon.However, if the device 401 is operated the concentration of chlorine gasis gradually increased, thereby the waste of the activated carbon issuppressed which prolongs its service life.

If the amount of activated carbon is increased more than that in theabove-described case, the wasting timing can be retarded. The reason whythe amount of the activated carbon is set at a small value is forshortening the testing time. The amount of the activated carbon is setat about 1 kg in the actually operated electrolytic testing machine 1.Granular nickel as a catalyst is wasted in the form of nickel oxide, asNaClO and NClO are decomposed. Even in this case, if the NaOHintroducing device 401 is used, the granular nickel has a prolongedlife.

In the treating device 6, the flow rate of the aqueous solution of NaCl11 flowing downstream from the chlorine gas purifying device 35 ismeasured by the flow rate sensor 36. Therefore, for example, if thechlorine gas purifying device 35 is not clogged and is operatingnormally, the flow rate sensor 36 measures a corresponding flow rate. Onthe other hand, if the chlorine gas purifying device 35 is clogged, theflow rate is decreased more than when the chlorine gas purifying device35 is operating normally. Therefore, the flow rate sensor 36 measuressuch a decreased flow rate.

With the above-described construction, an abnormality of the treatingsystem can be easily and reliably detected. In addition, since the flowrate sensor 36 is disposed downstream from the chlorine gas purifyingdevice 35, so that fine foreign matter entering the treating pipe line33 is caught by the chlorine gas purifying device 35, the operation ofthe flow rate sensor 36 cannot be obstructed by the foreign matter.Thus, the accuracy of the flow rate sensor 36 can be maintained over along period of time.

(2) Abnormal-point Detector in Treating System (FIGS. 4 to 6 and 35 to37)

Referring to FIG. 35, the flow rate sensor 36 has a function to transmitan abnormality signal which varies depending upon the type ofabnormality occurring in the treating system. A control means 213 isconnected to the flow rate sensor 36 and discriminates the type ofabnormality based on the abnormality signal from the flow rate sensor36. The contrast means 213 transmits an output signal corresponding tothe type of abnormality. An indicating means 214 is connected to thecontrol means 213 for indicating the type of abnormality correspondingto the output signal from the control means 213.

A memory means 215 is connected to the control means 213. An effectiverange of flow rate Q, namely, A2≦Q≦A1 which is a range between an upperlimit value A1 and a lower limit value A2 of flow rate, is previouslystored in the memory means 215, as shown in FIG. 36. Further, aprohibiting means 216 is connected to the control means 213 forprohibiting electric current to be supplied to the carbon electrodes 13in accordance with the output signal from the control means 213.

These means 213 to 216 are incorporated in the computer programmedcontrol unit 10 to constitute an abnormal-point detector 217 for thetreating system together with the flow rate sensor 36. The indicatingmeans 214 indicates, for example, a message which is displayed bycharacters on a liquid crystal display plate 131 on the upper surface ofthe left cover section 52 covering the control section C, as best shownin FIGS. 4 to 6. The prohibiting means 216 is operated to control the DCpower source 9 to its OFF state.

As shown in FIGS. 35 and 37, if a signal indicative of a command tostart the test is input, the flow rate sensor 36 measures a flow rate Q₁of the aqueous solution of NaCl 11 flowing in the treating pipe line 33.If the measured flow rate Q1 is in the effective range of A2≦Q₁ ≦A1, thecontrol means 213 determines that the flow rate sensor 36 istransmitting a normal signal and thus, the carbon electrodes 13 areenergized to start the corrosion test.

If the measured flow rate Q1 is larger than A1, the control means 213determines that the flow rate sensor 36 is transmitting an abnormalitysignal. The abnormality signal corresponds to the non-mounting of thecatalyst in the chlorine gas purifying device 35. Thus, a message "stopthe test because of the non-mounting of the catalyst" is indicated bythe indicating means 214, and electric current is prohibited from beingsupplied to the carbon electrodes 13 by the prohibiting means 216.

If the flow rate Q1 measured in the flow rate sensor 36 is smaller thanA2, operations similar to those described above are carried out.However, a message "stop the test" is indicated by the indicating means214, because the filter or catalyst is clogged, a circulationabnormality or the like has been produced.

The abnormal-point detector 217 for the treating system is controlled sothat it is operated even during the corrosion test.

Any problems of the treating system can be easily and reliably detectedby the detector 217 to precisely inform testing personnel of theproblem. The detector 217 is relatively inexpensive because of itssimple construction.

(3) Chlorine Gas Purifying Device (FIGS. 7, 9 and 38 to 40)

As best shown in FIG. 38, the chlorine gas purifying device 35 iscomprised of an outer shell 218 made of a synthetic resin, and a tubularcatalyst unit 219 accommodated in the outer shell 218. The outer shell218 is comprised of a bottomed tubular body 220 into which the catalystunit 219 is fitted, and a lid 223 capable of being attached to anddetached from an opening 221 in the body 220. The lid 223 closes theopening 221 to urge the catalyst unit 219 to a bottom wall 222 of thebody 220. The catalyst unit 219 is comprised of a tubular member 225made of a synthetic resin and having end walls 224 at opposite endsthereof, and an activated carbon 226 as a catalyst accommodated in thetubular member 225.

One of the end walls 224 and the bottom wall 222 of the bottomed tubularbody 220, e.g., an annular projection 227 located on the end wall 224 inthe illustrated embodiment, is fitted into the other, i.e., an annularrecess 228 provided in the bottom wall 222, so that an inlet 229 for theaqueous solution of NaCl, provided in the bottom wall 222 at a locationbetween the projection 227/recess 228 fit portions, communicates with athrough-hole 230 provided in the end wall 224. The through-hole 230,provided in the other end wall 224 of the catalyst unit 219,communicates with an outlet 232 for the aqueous solution of NaCl in aperipheral wall of the bottomed tubular body 220 through a passage 231in the lid 223.

In the outer shell 218, the bottomed tubular body 220 is comprised of acylinder 233 and a circular end plate 235. The end plate 235 is mountedto one end face of the cylinder 233 by a plurality of bolts 234 to formthe bottom wall 222. A liquid sealant is applied to one end face of thecylinder 233 against which the circular end plate 235 abuts. A connector237, made of a synthetic resin, is bonded to an outer surface of thecircular end plate 235 and has a through-hole 236 communicating with theinlet 229. A pipe 238, which is a portion of the treating pipe line 33,extends from the outlet 210 of the suction pump 34, as also shown inFIG. 9, and is connected to the connector 237.

The circular end plate 235 has a circular recess 239, provided in itsinner surface at a location between the annular recess 228, and a space240 for flowing of the aqueous solution of NaCl. The space 240 isdefined by cooperation of the circular recess 239 and the end wall 224of the catalyst unit 219. The space 240 communicates with the inlet 229and the through-hole 230.

The tubular member 225 of the catalyst unit 219 is comprised of acylinder 241 and a pair of circular end plates 242 mounted to openingsat opposite ends to form the end walls 224 and both end plates 242 havethe same structure. The circular end plate 242 includes an outer plate243 and an inner plate 244. The outer plate 243 has the annularprojection 227 on an outer periphery of its outer surface, and also hasan annular projection 245 fitted into and bonded in an opening in thecylinder 241 in the vicinity of an outer periphery of its inner surface.Further, the outer plate 243 has a plurality of openings 246, as alsoshown in FIG. 39, so that they open into an area surrounded by theannular projections 227 and 245. A net-like filter 248, made of asynthetic resin, is placed in the entire area surrounded by the innerannular projection 245 of the outer plate 243, and the inner plate 244having a plurality of openings 247 matched with the openings 246 in theouter plate 243 is fitted into and bonded in such an area. A pluralityof through-holes 230 are defined by the opposed openings 246 and 247 inthe inner and outer plates 244 and 243 for permitting the communicationbetween the flowing space 240 and the inside of the tubular member 225of the catalyst unit 219. A filter 248 is located in each of thethrough-holes 230.

As also shown in FIG. 40, the lid 223 includes a circular tubularportion 249, and a circular flange portion 250 connected to an outer endof the circular tubular portion 249. External threads 251 on an outerperipheral surface of the circular tubular portion 249 are threadedlyengaged with internal threads 252 on an inner peripheral surface of theopening 221 in the bottomed tubular body 220. A fitment 256, having ahexagonal head 255, is mounted to a projection 254 between a pair ofhalf moon-shaped recesses 253 located in an outer surface of thecircular flange portion 250. In carrying out the above-describedthreaded engagement, a tool is brought into engagement with thehexagonal head 255. A ring groove 257 is defined in the circular tubularportion 249 on the side of the flange portion 250. The circular tubularportion 249 and the opening 221 in the bottomed tubular body 220 aresealed therebetween by a seal ring 258 made of a rubber and mounted inthe ring groove 257.

The circular tubular portion 249 has a circular recess 259 in its innersurface, and an NaCl aqueous solution flowing space 260 is defined bycooperation of the circular recess 259 and the end walls 224 of thecatalyst unit 219 to communicate with the through-holes 230. A pluralityof projections 261 are disposed at equal distances around the circularrecess 259, so that an end face of each of the projections 261 is urgedagainst the end wall 224 of the catalyst unit 219. That portion of anouter peripheral surface of the circular tubular portion 249, which isbetween the external threads 251, is formed into a tapered surface 264.A flowing space 265 is defined between the tapered surface 264 and aninner peripheral surface of the bottomed tubular body 220 to communicatewith the outlet 232. A space 266 is defined between the adjacentprojections 261 and communicates with the flowing spaces 260 and 265.Therefore, the flowing spaces 260 and 265 and the space 266 form thepassage 231.

A connector 268, made of a synthetic resin and having a through-hole 267communicating with the outlet 232, is bonded to the outer peripheralsurface of the bottomed tubular body 220. A pipe member 269, of thetreating pipe line 33, is connected to the connector 268, as shown inFIG. 9.

In the outer shell 218, the inlet 229 and the outlet 232 are disposed onopposite sides of an axis of the outer shell 218.

As best shown in FIG. 9, the chlorine gas purifying device 35 isdisposed on the machine base 44 through the support 208 in an inclinedmanner such that the outlet 232 thereof lies at an upper location andthe inlet 229 thereof lies at a lower location. In this case, theinclination angle β is set at a value such that when the aqueoussolution of NaCl 11 within the bottomed tubular body 220 has beenwithdrawn from the inlet 229 through the suction pump 34 and thedrainage pipe 211 for the purpose of replacing the catalyst unit 219,the liquid level of the remaining aqueous solution of NaCl 11 lies belowthe opening 221 in the body 220.

If the chlorine gas purifying device 35 is constructed in theabove-described manner, the aqueous solution of NaCl 11 including thechlorine gas is reliably introduced into the catalyst unit 219 withoutentering from the inlet 229 and without being between the outerperipheral surface of the tubular member 225 of the catalyst unit 219and the inner peripheral surface of the bottomed tubular body 220 of theouter shell 218, by virtue of a labyrinth structure formed by therecess-projection fit portions 228 and 227. Therefore, it is possible toenhance the purification rate of the chlorine gas.

In this case, the catalyst unit 219 is urged against the bottom wall 222of the outer shell 218 by the lid 223. Hence, the labyrinth structure isreliably formed and maintained. The closure of the labyrinth structureis easily determined by the condition of mounting of the lid 223 to thebottomed tubular body 220. For example, the incomplete closure of thelabyrinth structure is confirmed by the fact that the seal ring 258 canbe viewed from a gap between the flange portion 250 and the body 220.

The chlorine gas purifying device 35 is disposed in the inclined mannersuch that the outlet 232 is turned upwards, as described above.Therefore even when the unpurified chlorine gas is present in the device35, the accumulation of the unpurified chlorine gas can be inhibited tothe maximum extent.

Moreover, since the provision of the outlet 232 is not in the lid 223,the mounting and removal of the lid 223 can be easily performed, and theformation of the lid 223 and the catalyst into one unit ensures that theoperation of replacing the catalyst can be efficiently performed. Inaddition, even if the lid 223 is removed from the bottomed tubular body220 after withdrawal of water, the dropping of the remaining aqueoussolution of NaCl from the opening 221 in the body 220 can be preventedby the inclined disposition of the chlorine gas purifying device 35.

The opposite end walls 224 in the catalyst unit 219 have the samestructure. Hence, in fitting the catalyst unit 219 into the bottomedtubular body 220 to fit the annular projection 227 into the annularrecess 228, the catalyst unit 219 may be fitted into the body 220 fromeither end wall 224. Thus, it is easy to mount the catalyst unit 219.

The labyrinth structure in the chlorine gas purifying device 35 may beomitted in some cases.

(4) Determining Device for Determining Timing of Replacement of Catalyst(FIGS. 4 to 6, 41 and 42)

The purifying capability of the activated carbon 226, which is used asthe catalyst, is decreased in accordance with the product of theelectric current flowing across the carbon electrode 13 and time.Therefor, in order to replace the activated carbon 226 by a newactivated carbon 226, e.g., the catalyst unit 219 in this embodimentbefore the purifying capability of the activated carbon 226 in serviceis completely lost, a determining device 270 is mounted in theelectrolytic test machine 1. The determining device 270 is incorporatedin the computer programmed control unit 10.

FIG. 41 is a block diagram of the determining device 270, and FIG. 42 isa flow chart illustrating the operation of the determining device 270.The term "set test conditions" in FIG. 42 means that any of thefollowing testes are selected: a) the corrosion test including thecoating film peeling-off step and the steel plate corroding step, b) thecoating film peeling-off test, and c) that the test is to be finished.Conditions selected are then input.

Referring to FIG. 41, the determining device 270 includes a capabilitystorage means 271 for storing the purifying capability of the activatedcarbon 226 in the form of an effective current amount C₁ which is aproduct I₁ ·T₁ of a certain current I₁ flowing across the carbonelectrode 13 and a total test time T₁ usable when the current I₁continues to flow. A memory means 276 stores the effective currentamount C₁ in the form of a remaining current amount C₄. A currentmeasuring means (ammeter) 29 measures a current I₂ flowing across thecarbon electrode 13 during a test. A time measuring means 273 measures atest time T₂. A first calculating means 274 calculates a used currentamount C₂ which is a product I₂ ·T₂ Of the current I₂ and the test timeT₂. A second calculating means 275 subtracts the used current amount C₂from the remaining current amount C₄ to provide a new remainingeffective current amount and stores the latter in the memory means 276.An input means 277₁ inputs a maximum current I₃ of the DC power source 9at the start of the test. A memory means 277₂ stores a test time T₃. Athird calculating means 278 calculates a presupposed used current amountC₅ which is a product I₃ ·T₃ of the maximum current I₃ and the test timeT₃. A control means 279 compares the remaining effective current amountC₄ and the presupposed used current amount C₅ with each other andtransmits a catalyst replacing signal, when C₄ <C₅.

If the determining device 270 is constructed in the above manner, it ispossible, before the test is carried out, to automatically detect thatthe replacement time of the activated carbon 226 has been reached due toa decrease in purifying capability of the activated carbon 226.

The determining device also includes a) a message indicating means 280adapted to inform testing personnel that the catalyst replacing timinghas been reached based on the catalyst replacing signal from the controlmeans 279, and b) a prohibiting means 281 which prohibits current to besupplied to the carbon electrodes 13.

As best shown in FIGS. 4 to 6, a message indicated in the messageindicating means 280 is displayed on a liquid crystal display plate 131mounted on the upper surface of the left cover section 52 covering thecontrol section C. The prohibiting means 281 is operated to maintain theDC power source 9 in its OFF state. Thus, testing personnel can reliablyknow the replacement time of the activated carbon 226.

As shown in FIG. 42, the determining device 270 is constructed so thatthe device 270 will not operate after replacement of the catalyst unit219 unless the remaining effective current amount C₄ stored in thememory means 276 is reset to a relation of C₄ =C₁.

If the remaining effective current amount C₄ and the presupposed usedcurrent amount C₅ are in a relation of C₄ ≧C₅ prior to starting thetest, the test is started, and the calculation of the used currentamount C₂ and the like are carried out.

N. Exhaust Device

(1) Entire Structure and Function thereof (FIGS. 7 to 9 and 43 to 46)

As described above, chlorine gas is generated around the carbonelectrodes 13 in the corrosion test. Most of the chlorine gas iscollected and purified by the chlorine gas treating device 6 describedabove. A portion of the chlorine gas is released out of the aqueoussolution of NaCl and flows above the liquid level f. The exhaust device7 is mounted in the electrolytic test machine to collect the releasedchlorine gas.

As best shown in FIGS. 9 and 43, the exhaust fan 39 of the exhaustdevice 7 is fixed on a mounting base 284 which is supported by an upperangle member 282 of the frame 90 and a support pillar 283. An intakepipe 285, extending from the inlet of the exhaust fan 39 in the exhaustpipe line 37, is passed through the right sidewall portion 49 of theelectrolytic cell 12 to communicate with the inside of the electrolyticcell 12 above the liquid level f of the aqueous solution of NaCl 11. Acap-like grill 287, made of a synthetic resin, is detachably mounted toan inlet 286 of the intake pipe 285. A discharge pipe 288, extendingfrom the outlet of the exhaust fan 39 in the exhaust pipe line 37,extends downwards and opens into the atmosphere in the vicinity of thewater dispensing block 82.

On the suction side of the exhaust fan 39 in the exhaust pipe line 37,namely, in the intake pipe 285, an adsorbing member 38 for adsorbingchlorine gas is disposed at an upstream location. A detecting means 40,for detecting an abnormality of the exhaust system, is disposed at adownstream location. The adsorbing member 38 has a structure similar tothat of the catalyst unit 219 and hence, includes activated carbon, hasa permeability, and is formed into a single unit. When the grill 287 isremoved from the inlet 286 of the intake pipe 285, the adsorbing member38 can be placed into the intake pipe 285 through the inlet 286.

The detecting means 40 includes a detecting pipe 290 made of a syntheticresin and mounted between the intake pipe 285 and the electrolytic cell12, and a water level sensor D mounted in the detecting pipe 290, asbest shown in FIGS. 43 and 44. The detecting pipe 290 communicates atits upper end with a downstream portion of the intake pipe 285, and atits lower end with a zone of the electrolytic cell 12 in which theaqueous solution of NaCl 11 is stored. A sensor portion of the waterlevel sensor D is disposed above a liquid level f₁ in the detecting pipe290, which is the same level as the liquid level f in the electrolyticcell 12.

In the above-described construction, if the exhaust fan 39 is operated,the chlorine gas flowing above the liquid level f in the electrolyticcell 12 is adsorbed in the activated carbon when passed through theadsorbing member 38, and thus, clean air is discharged to the atmospherethrough the exhaust pipe 288.

FIG. 45 illustrates the relationship between the test time and theconcentration of chlorine gas above the liquid level f within theelectrolytic cell 12, a) when the exhaust device 7 was not operated andthe chlorine gas treating device 6 described above was operated, and b)when the device 6 was brought into a non-operated state. Test conditionswere such that an electric current of 50 A was continuously supplied,the amount of the activated carbon was 550 g (corresponding to the caseshown in FIG. 34), and the temperature of the aqueous solution of NaCl11 was 45° C. As apparent from FIG. 45, if the chlorine gas treatingdevice 6 is operated under the non-operation of the exhaust device 7,the concentration of the chlorine gas can be maintained at an extremelylow level, but if the exhaust device 7 is operated, the concentration ofthe chlorine gas can be further lowered.

To confirm an effect of the exhaust device when activated carbon is usedas the adsorbent of the adsorbing member 38, the outlet of the exhaustpipe 288 was put into communication with the inside of the electrolyticcell 12 above the liquid level f in the electrolytic cell 12, and atest, which involves circulating the inside gas above the liquid level fthrough the adsorbent, was carried out.

FIG. 46 illustrates the relationship between the test time and theconcentration of the chlorine gas above the liquid level f within theelectrolytic cell 12. Conditions for the test were such that an electriccurrent of 20 A was continuously supplied, the amount of the activatedcarbon was 550 g (corresponding to the case shown in FIG. 34), and thetemperature of the aqueous solution was 45° C. In this case, the exhaustfan 39 was not operated for a period from the start of the test untilthe test time reached 50 hours. The concentration of the chlorine gasrelatively steeply rose for such a period and reached about 18 ppm aftera lapse of 50 hours. If the exhaust fan 39 was operated thereafter, theconcentration of chlorine gas was extremely decreased by the purifyingeffect of the adsorbent and eventually reached 0.5 ppm or less. Thus,with use of the exhaust device 7 having one end of the exhaust pipe 288open to the atmosphere, the concentration of the chlorine gas above theliquid level f within the electrolytic cell 12 and the concentration ofthe chlorine gas discharged to the atmosphere are further decreased andsuppressed at least to 0.5 ppm or less.

In the above-described construction, for example, if the adsorbingmember 38 is operating normally, a corresponding negative pressure isgenerated in the downstream portion of the intake pipe 285, and theliquid level f₁ within the detection pipe 290 rises to a level equal toor higher than the position of the water level sensor D due to thenegative pressure, as shown by a dashed line in FIG. 44. Thus, the waterlevel sensor D detects that the exhaust system is operating normally. Onthe other hand, during replacement of the adsorbing member 38, if a newadsorbing member 38 is not disposed within the intake pipe 285 such asdue to forgetting to mount a replacement adsorbing member 38, thenegative pressure is considerably lower than under normal operatingconditions. Therefore, the liquid level f₁ is below the water levelsensor D, and this state is detected by the water level sensor D.

According to such a construction, an abnormality of the exhaust systemcan be easily and reliably detected.

(2) Abnormal-point Detector for Exhaust System (FIGS. 4 to 6, 47A, 47Bto 49)

As shown in FIGS. 47A and 47B, the detecting means 40 transmits anabnormality signal which varies depending upon the type of abnormalityof the exhaust system. First and second water level sensors D₁ and D₂are disposed at locations indicating the lower limit value L1 and theupper limit value L2 of the water level L in the detection pipe 290,respectively. A control means 291 is connected to the first and secondwater level sensors D₁ and D₂ in the detecting means 40 anddiscriminates the type of abnormality based on the abnormality signalsfrom the first and second water level sensors D₁ and D₂. The controlmeans 291 transmits an output signal corresponding to the type ofabnormality. An indicating means 292 is connected to the control means291 and indicates the type of abnormality in accordance with the outputsignal from the control means 291. A prohibiting means 294 is connectedto the control means 291 and prohibits electric current to be suppliedto the carbon electrodes 13 based upon the output signal from thecontrol means 291.

These means 291, 292 and 294 are incorporated in the computer programmedcontrol unit 10 to constitute an abnormal-point detector 295 for theexhaust system together with the first and second water level sensors D₁and D₂. The indicating means 292 indicates, for example, a message,which is displayed by characters on a liquid crystal display plate 131mounted on the upper surface of the left cover section 52 covering thecontrol section C, as best shown in FIGS. 4 to 6. The prohibiting means294 is operated to maintain the DC power source 9 in its OFF state.

As shown in FIGS. 47A, 47B, 48 and 49, if a signal indicative of acommand to start the test is input, one of the first and second waterlevel sensors D₁ and D₂ detects a water level depending upon thenegative pressure in the intake pipe 285. If the detected water level L₃is in an acceptable range of L₁ ≦L₃ <L₂, the first water level sensor D₁is in its ON state, and the control means 291 determines that the firstwater level sensor D₁ is transmitting a normal condition signal.Therefore, an electric current is supplied to the carbon electrodes 13to start the corrosion test.

If the detected water level L₃ is lower than L₁, the first water levelsensor D₁ is in its OFF state, and the control means 291 determines thatthe first water level sensor D₁ is not transmitting the normal conditionsignal. That is, the sensor D₁ is transmitting an abnormality signal,which corresponds to the non-mounting of the adsorbing member 38 and thenon-operation of the exhaust fan 39, whereby the control means 291,transmits a corresponding output signal. Thus, a message "stop the testbecause of the non-mounting of the adsorbing member 38 or thenon-operation of the exhaust fan 39" is indicated by the indicatingmeans 292, and current supply to the carbon electrodes 13 is prohibitedby the prohibiting means 294.

If the detected water level L₃ is equal to or higher than L₂, the secondwater level sensor D₂ is in its ON state, and the control means 291determines that the second water level sensor D₂ is transmitting anabnormality signal, which corresponds to indicating that the adsorbingmember 38 is clogged. The control means 291 transmits a correspondingoutput signal. Thus, because the adsorbing member 38 is clogged, amessage "stop the test because of the clogging of the adsorbing member38" is indicated by the indicating means 292, and the current supply tothe carbon electrodes 13 is prohibited by the prohibiting means 294.

The abnormal-point detector 295 for the exhaust system is controlled sothat it is operated even during the corrosion test.

The detector 295 enables problems on the exhaust system to be easily andreliably detected so that testing personnel can be informed thereof. Inaddition, the detector 295 has a simple construction and hence, isrelatively inexpensive.

Only the indicating means 292 may be connected to the control means 291.In addition, in place of the water level sensors D₁ and D₂, adiaphragm-type negative pressure sensor, an air flow sensor, a windspeed sensor or the like may be used.

(3) Modification to Exhaust Device (FIG. 50)

A detection pipe 296, made of the synthetic resin, is comprised of firstand second pipe portions 297 and 298 extending vertically, and a thirdpipe portion 299 which connects lower ends of the first and second pipeportions 297 and 298 to each other. An upper end of the first pipeportion 297 communicates with the downstream portion of the intake pipe285, and an upper folded end of the second pipe portion 298 communicateswith the first pipe portion 297 at a location lower than the upper endof the first pipe portion 297. A water supply pipe line 17₁, which ismade of a synthetic resin pipe material, is connected to the third pipeportion 299 and is also connected to a cock 30₁ of a water serviceinlet.

A water level sensor D, similar to the sensor described above, ismounted in the first pipe portion 297 to lie above the liquid level f₁.A float valve 300 is accommodated in the first pipe portion 297. A valveseat 301 of the float valve 300 is formed at a communication portion ofthe first pipe portion 297 with the intake pipe 285.

A tube 302, made of a soft synthetic resin, is connected to the upperend of the second pipe portion 298, and extends into the electrolyticcell 12. The tube 302 is used for supplying water to the electrolyticcell 12 and for washing the electrolytic cell 12.

A solenoid valve 31₁, similar to the solenoid valve 31 described above,is mounted at an intermediate portion of the water supply pipe line 17₁.The water supply pipe line 17 in the above-described example iseliminated by mounting of the water supply pipe line 17₁.

Water is supplied to the electrolytic cell 12 through the detection pipe296 from the water supply pipe line 17₁. The liquid level f₁ in thefirst pipe portion 297 is defined at the same position as a liquid levelf₂ at the upper folded portion of the second pipe portion 298 by waterflowing from the upper folded end of the second pipe portion 298 intothe electrolytic cell 12.

During supplying of water to the electrolytic cell 12, if watersubstantially fills up the first pipe portion 297 due to the force ofwater, the clogging of the tube 302 or the like, the float valve 300 isseated onto the valve seat 301 to prevent water from flowing toward theexhaust fan 39. The same is true when the inside of the electrolyticcell 12 is washed through the tube 302.

A sensor portion of the water level sensor D is immersed in tap waterwhen the liquid level f₁ rises. Hence, the sensor portion can be keptclean, The chlorine gas flowing above the liquid level f in theelectrolytic cell 12 is prevented from leaking to the outside by a trapeffect of the detecting pipe 296.

O. Overflow Device having Adsorbing Function (FIGS. 7, 8, 13, 14 and 51)

The overflow device 8 is mounted in the electrolytic test machine 1 inorder to discharge an extra amount of the aqueous solution of NaCl whenthe amount of the aqueous solution of NaCl 11 exceeds a defined valuedue to a problem with the water level sensor 15 which is placed in theelectrolytic cell 12 on the intake side corresponding to the exhaustdevice 7.

As best shown in FIGS. 8, 13 and 51, the overflow pipe 41 is comprisedof a folded pipe section 304 having a vertical portion 303 extendingalong the outer surface of the rear wall portion 71 of the electrolyticcell 12, and a horizontal inlet-side pipe section 305 which is connectedto an upper end of the vertical portion 303 and which has a diameterlarger than that of the vertical portion 303. The horizontal inlet-sidepipe section 305 passes through the rear wall portion 71 of theelectrolytic cell 12 and is connected to the space above the liquidlevel f. As shown in FIGS. 8 and 14, the folded pipe portion 304 isconnected at its lower end to the drainage portion 82b of the waterdispensing block 82.

In a portion of the inlet pipe section 305 which protrudes from theelectrolytic cell 12, substantial half of the inlet pipe section 305 isnotched from an outer end to an intermediate portion, so that the inletpipe section 305 is also used as an intake pipe. Thus, the gas intakeport 42 is defined in the inlet pipe section 305. A net 306, forremoving foreign matter, is mounted on a peripheral portion of the gasintake port 42 to cover the gas intake port 42.

The adsorbing member 43 for adsorbing the chlorine gas is disposed inthe inlet pipe section 305 at a place closer to an inlet 307 than to thegas intake port 42. The adsorbing member 43 has a structure similar tothat of the catalyst unit 219 and hence, includes activated carbon, hasan air/water permeability and is formed as a single unit. Therefore, acap-like grill 308, made of a synthetic resin, is attachable to anddetachable from the inlet 307 of the inlet pipe section 305. When thegrille 305 is removed from the inlet pipe section 305, the adsorbingmember 43 can be placed into the inlet pipe section 305 through theinlet 307.

In the above-described construction, if the amount of the aqueoussolution of NaCl 11 within the electrolytic cell 12 exceeds the definedvalue, the extra amount of the aqueous solution is discharged from theinlet 307 through the adsorbing member 43 and the overflow pipe 41 tothe water dispensing block 82. In this case, the aqueous solution ofNaCl 11 flows in the lower portion of the inlet pipe section 305 andhence, the solution does not flow out from the gas intake port 42.

The suction of the gas into the electrolytic cell 12, produced by theoperation of the exhaust device 7, is performed through the gas intakeport 42 and the inlet pipe section 305. The chlorine gas, which flowsabove the liquid level f during non-operation of the exhaust device 7,is inhibited from leaking out of the electrolytic cell 12 by theadsorbing member 43.

P. Other Example of Determining Device for Determining Timing ofReplacement of Carbon Electrode (FIGS. 4 to 6, 52 and 53)

FIG. 52 is a block diagram of the determining device 123 and FIG. 53 isa flow chart illustrating the operation of the determining device 123.The term "set test conditions" in FIG. 53 means that any of thefollowing conditions are selected: a) the corrosion test including thecoating film peeling-off step and the steel plate corroding step, b) thecoating film peeling-off test, and c) the test is to be finished.Conditions selected are then input.

Referring to FIG. 52, the determining device 123 includes a life storingmeans 124 for storing a service life of the carbon electrode 13 as aneffective current amount C₁ which is product I₁ ·T₁ of a certain currentI₁ flowing across the carbon electrode 13 and a total test time T₁usable when the current I₁ continues to flow. A memory means 311 storesthe effective current amount C₁ as a remaining effective current amountC₄. A current measuring means (ammeter) 29 measures a current I₂ flowingacross the carbon electrode 13 during a test. A time measuring means 125measures a test time T₂. A first calculating means 132₁ calculates aused current amount C₂ which is a product I₂ ·T₂ Of the current I₂ andthe test time T₂. A second calculating means 310 subtracts the usedcurrent amount C₂ from the remaining effective current amount C₄ toprovide a new remaining effective current amount and stores it in thememory means 311. A control means 312 evaluates the remaining effectivecurrent amount C₄ at the start of the test and transmits an electrodereplacing signal when C₄ ≦0.

If the determining device 123 is constructed in the above manner, it ispossible to automatically detect the replacement time, as the servicelife of the carbon electrode 13, which is a consumable electrode,reaches the end of its service life.

In this case, even if the remaining effective current amount C₄ issmaller than 0, the test is continued. This is permitted by depending ona margin of the effective current amount C₁ corresponding to severalruns of the test.

The determining device 123 also includes a) a message indicating means129 adapted to inform testing personnel that the replacement time of theelectrode has been reached, based on the electrode replacing signal fromthe control means 312, and b) a prohibiting means 130 for prohibitingcurrent to be supplied to the carbon electrode 13.

As best shown in FIGS. 4 to 6, the message provided by the messageindicating means 129 is displayed by characters on the display plate 131mounted on the upper surface of the left cover section 52 covering thecontrol section C as described above. The prohibiting means 130 isoperated to maintain the DC power source 9 in its OFF state. Thus,testing personnel can reliably know the replacement time of the carbonelectrode 13.

As shown in FIG. 53, the determining device 123 is constructed so thatthe device 123 will not operate unless the remaining effective currentamount C₄ stored in the memory means 311 is reset to a relation of C₄=C₁.

If the remaining effective current amount C₄ is larger than 0 prior tostarting the test, the test is started, and the calculation and theintegration of the used current amount C₂ and the like are carried out.

The determining device 123 includes a remaining effective current amountindicating means 313 for indicating the remaining effective currentamount C₄ of the carbon electrode 13. The remaining effective currentamount C₄ indicated by the remaining effective current amount indicatingmeans 313 is displayed as a bar graph on the liquid crystal displayplate 131 such that the remaining effective current amount C₄ isgradually decreased, as shown in FIG. 24, as described above. Thus,testing personnel can easily know the remainder and varying situation ofthe service life of the carbon electrode 13.

Q. Another Example of Determining Device for Determining Timing ofReplacement of Catalyst (FIGS. 4 to 6, 54 and 55)

(1) Referring to FIG. 54, the determining device 270 includes acapability storing means 271 for storing a purifying capability of anactivated carbon 226 as an effective current amount C₁ which is aproduct I₁ ·T₁ of a certain current I₁ flowing across the carbonelectrode 13 and a total test time T₁ usable when the current I₁continues to flow. A current measuring means (ammeter) 29 measures acurrent I₂ flowing across the carbon electrode 13 during a test. A timemeasuring means 273 measures a test time T₂. A first calculating means274 calculates a used current amount C₂ which is a product I₂ ·T₂ of thecurrent I₂ and the test time T₂. An integrating means 314 integrates theused current amount C₂. A memory means 315 stores the integration usedcurrent amount C₃. A second calculating means 316 subtracts theintegration used current amount C₃ from the effective current amount C₁to provide a remaining effective current amount C₄. An input means 277₁inputs a maximum current I₃ in the DC power source 9 at the start of thetest. A memory means 277₂ stores a test time T₃. A third calculatingmeans 278 calculates a presupposed used current amount C₅ which is aproduct I₃ ·T₃ of the maximum current I₃ and the test time T₃. A controlmeans 279 compares the remaining effective current amount C₄ and thepresupposed used current amount C₅ with each other and transmits acatalyst replacing signal when C₄ <C₅.

If the determining device 270 is constructed in the above manner, it ispossible before the test is carried out to automatically detect that thereplacement time of the activated carbon has been reached due to adecrease in purifying capability of the activated carbon 226.

The determining device 270 also includes a) a message indicating means280 adapted to inform testing personnel that the replacement time of theelectrode has been reached, based on the catalyst replacing signal fromthe control means 279, and b) a prohibiting means 281 for prohibitingcurrent to be supplied to the carbon electrode 13.

As best shown in FIGS. 4 to 6, the message provided by the messageindicating means 280 is displayed by characters on the display plate 131mounted on the upper surface of the left cover section 52 covering thecontrol section C such as described above. The prohibiting means 281 isoperated to maintain the DC power source 9 in its OFF state. Thus,testing personnel can reliably know the replacement time of theactivated carbon electrode 13.

The determining device 270 is constructed such that the device 270 willnot operate unless the integration used current amount C₃ is reset inthe memory means 315 to 0 after the catalyst unit 219 is replaced.

If the acceptable used current amount C₆ and the integration usedcurrent amount C₃ are in a relation of C₆ ≧C₃ prior to starting thetest, the test is started, and the integration of the used currentamount C₂ and the like are carried out.

Although the embodiments of the present invention have been described indetail, it will be understood that the present invention is not limitedto the above-described embodiments, and various modifications may bemade without departing from the spirit and scope of the inventiondefined in the claims.

What is claimed is:
 1. An electrolytic test machine comprising:anelectrolytic cell in which an aqueous solution of NaCl is stored so thata test material is immersed in the aqueous solution of NaCl; anelectrode immersed in the aqueous solution of NaCl; a DC power sourcefor supplying electric current between said electrode and said testmaterial; a chlorine gas treating device for collection, out of theaqueous solution of NaCl, a) chlorine gas which is generated around saidelectrode with electrolysis of the aqueous solution of NaCl and b)aqueous solution of NaCl; a chlorine gas collecting hood which covers aportion of said electrode, wherein said chlorine gas collecting hood isentirely disposed within the aqueous solution of NaCl; and a suctionport is located below said chlorine gas collecting hood.
 2. Anelectrolytic test machine according to claim 1, wherein said chlorinegas treating device includes a treating pipe line leading to saidsuction port, a suction pump disposed in said treating pipe line, and achlorine gas purifying member disposed in said treating pipe line andsaid chlorine gas purifying member having a catalyst which decomposesNaClO and HClO which are reaction products in a test.
 3. An electrolytictest machine according to claim 2, further including an NaOH introducingdevice mounted in said electrolytic cell for introducing NaOH, producedin a test material immersion zone within said electrolytic cell, to saidelectrode immersion zone.
 4. An electrolytic test machine according toclaim 2, wherein said suction port is inclined.
 5. An electrolytic testmachine according to claim 1, further including an NaOH introducingdevice mounted in said electrolytic cell for introducing NaOH, producedin a test material immersion zone within said electrolytic cell, to anelectrode immersion zone.
 6. An electrolytic test machine according toclaim 1, wherein said chlorine gas collecting hood has an inclined roof.